Method for providing corrosion protection to a pressurized water-steam system

Abstract

The present invention relates to a method for providing corrosion protection to a pressurized water-steam system using extremely low amounts of N-acyl sarcosine or its salts, and also to a method for determining the concentration of N-acyl sarcosine in an aqueous solution or emulsion.

Description

[0001] The present invention relates to a method for providing corrosion protection to a pressurized water-steam system using extremely low amounts of N-acyl sarcosine or its salts.

[0002] The present invention also relates to a method for determining the concentration of N-acyl sarcosine in an aqueous solution or emulsion. Background of the Invention

[0004] Water-steam systems, in particular water-steam circuits and generally steam generators, such as those in power plants, require water treatment to prevent corrosion damage to surfaces in contact with water.

[0005] Organic water additives based on film-forming amines (FFAs) provide excellent corrosion protection to water-steam systems. This is particularly applicable to devices operating in a cyclic mode, where corrosion protection is required during shutdown periods and protection of components in contact with water and in the dry state must be maintained. Film-forming amines are characterized in that they carry at least one long-chain alkyl or alkenyl group and have one or more amino groups. Film-forming amines form a protective layer between the metal or metal oxide surface and the corrosive medium. It is speculated that the polar amino group chemisorbs onto the metal (oxide) surface, and the lipophilic long-chain alkyl or alkenyl group renders the surface non-wettable by water, thereby blocking corrosive substances.

[0006] However, from the perspective of power plant manufacturers or operators, any organic matter in the steam-water cycle poses a risk of harmful side effects. Possible side effects include corrosive degradation products, interference with the monitoring of cationic conductivity, effects on boiling and condensation, or fouling. Organic amines, for example, produce volatile acidic degradation products, which lower the pH and thus promote corrosion (although the amino groups of the intact amine may counteract the acidity to some extent). Therefore, it is desirable to limit the general use of organic additives to the minimum possible amount.

[0007] In any case, it is not possible to limit the concentration of FFAs beyond a certain limit without an unacceptable loss of activity.

[0008] Another concern regarding FFAs is their toxicity. Oleylamine, for example, is classified as a health and environmental hazard. It can cause organ damage through long-term or repeated exposure and can be fatal if swallowed or inhaled. In addition, it is highly toxic to aquatic life and has a long-lasting effect. Although such risks may be manageable, for example, in the closed steam-water circuits of power plants, it is obvious that for water-steam cycles directly or indirectly used in food, cosmetic, or pharmaceutical processing, it is best to avoid such hazards. In systems where there is no direct or indirect contact with materials with unacceptable toxicity, it is also best to avoid using harmful materials because water will ultimately be released into the environment. This is especially true for geothermal systems, such as geothermal power plants or geothermal heating units, where after power generation / heating, water is released into the environment, usually deep underground, where its further movement and impact, such as entering groundwater, cannot be controlled.

[0009] N-acyl sarcosines are carboxamides of carboxylic acids and sarcosine (N-methylglycine). They have been described as components of corrosion inhibitor compositions.

[0010] DE-A-1916628 describes a mixture containing A) 57 - 89.5 wt% of the product obtained by reacting sulfonyl chloride with ammonia or a lower aliphatic primary amine and then with a halogen carboxylic acid, or the reaction product of sulfonyl chloride with an aminocarboxylic acid having 2 - 9 carbon atoms in the presence of a base; or salts of these reaction products; B) 5 - 30 wt% of a fatty acid acyl sarcosinate having an alkali metal or ammonium counterion; C) 5 - 10 wt% of cyclohexylamine; and D) 0.5 - 3 wt% of benzotriazole and / or 2-mercaptobenzothiazole as corrosion inhibitors. The mixture is added in an amount of 0.05 - 5 wt%; corresponding to an amount of at least 25 ppm of sarcosinate. In the examples, when used in the form of the claimed composition, the sarcosinate is used in an amount of 250 - 750 ppm. In the comparative examples, when used alone, the dose is 5000 ppm. In the examples, a pressurized system is not used.

[0011] JP S57-185988 relates to a corrosion protection composition comprising polymaleic acid or its salt and a sarcosine compound R-C(O)-N(CH3)-CH2-COOH, where R is a C8-C 22 -hydrocarbyl group. In the examples, when used in the form of the claimed composition, the sarcosine compound is used in an amount of 4 - 30 ppm. In the comparative examples, when used alone, the dose is 40 ppm. In the examples, mild steel specimens are rotated in test water at 50 °C or 90 °C for 5 days. A pressurized system is not described or used. The corrosion protection effect is only tested on steel specimens in boiler water and on the walls of beakers containing boiling test water. The corrosion protection behavior in steam or condensate or in components in contact with them is not tested.

[0012] EP-A-1092788 relates to a corrosion inhibition preparation which contains acyl amino acids and triazole derivatives. The definition of acyl amino acids includes N-acyl sarcosine. In the examples, the preparation is used in a total amount of 0.2% by weight. Taking into account the mixing ratio of N-acyl sarcosine and triazole derivatives given in Table 1 of this reference, N-acyl sarcosine is used in an amount of about 0.09 to 0.13% by weight (corresponding to 900 - 1300 ppm). Summary of the Invention

[0014] The object of the present invention is to provide a corrosion inhibitor which can achieve corrosion protection in a pressurized water-steam system with a significantly lower amount of active agent. When the reagent is added only to the feed water, it also provides corrosion protection, in particular, to those system components which are in contact with steam and condensate. In addition, the reagent should be non-toxic or at least significantly less toxic than FFAs. Effective corrosion protection should also be achievable with the reagent used alone or at most in combination with alkalized amines; that is, the mixing partners of the compositions of DE-A-1916628, JP S57-185988 and EP-A-1092788 should not be necessary to achieve these effects.

[0015] This object is achieved by using certain N-acyl sarcosinates in a (total) amount of at most 10 ppm as corrosion inhibitors.

[0016] The present invention thus relates to a method for providing corrosion protection to a pressurized water-steam system, which method comprises adding an N-acyl sarcosine compound of formula (I) or a mixture of different N-acyl sarcosine compounds of formula (I) or a salt thereof

[0017] R-C(=O)-N(CH3)-CH2-COOH (I)

[0018] wherein R is a straight-chain or branched acyclic hydrocarbon group having 10 to 24 carbon atoms; wherein in the case of using a mixture of different N-acyl sarcosine compounds of formula (I), in up to 30% by weight of the N-acyl sarcosine compound (I) based on the total weight of the mixture, R can also be a straight-chain or branched acyclic hydrocarbon group having 4 to 9 carbon atoms;

[0019] wherein the N-acyl sarcosine compound of formula (I), the mixture of different N-acyl sarcosine compounds of formula (I) or a salt thereof is added to the water used for operating the water-steam system in an amount such that the average total concentration of the one or more compounds of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 10 mg / kg.

[0020] The present invention also relates to the use of an N-acylsarcosine compound or a mixture of N-acylsarcosine compounds of formula (I) or a salt thereof, as defined above and below, for providing corrosion protection to a pressurized water-steam system, wherein said use comprises adding an N-acylsarcosine compound or a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof to the water used for operating the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 10 mg / kg, preferably in the range of 0.01 to 8 mg / kg, more preferably in the range of 0.02 to 6 mg / kg, especially in the range of 0.02 to 5 mg / kg, more especially in the range of 0.05 to 5 mg / kg, even more especially in the range of 0.1 to 5 mg / kg, such as in the range of 0.5 to 5 mg / kg; in particular in the range of 0.1 to 3.5 mg / kg, more particularly in the range of 0.5 to 3.5 mg / kg, even more particularly in the range of 0.5 to 3 mg / kg, very particularly in the range of 0.8 to 2.5 mg / kg.

[0021] Another object is to provide a method for determining the concentration of a corrosion inhibitor present in a pressurized water-steam system. Long-term experience with FFAs has shown that over time, depletion of the corrosion inhibitor concentration can occur. Therefore, monitoring the concentration is an important tool for safely and efficiently controlling corrosion. The effectiveness of the treatment is usually controlled by measuring the residual corrosion inhibitor in the aqueous phase of the water-steam circulation system, which is an indirect proof that the surface is fully protected.

[0022] The methods contemplated for this purpose are, for example, titration, voltamperometry, spectrophotometry, sensor-based methods, flow injection methods or chromatography. Although chromatography is very sensitive and precise, they are too complex and expensive for most uses. Spectrophotometry is a good compromise. Spectrophotometry for determining the concentration of substances that do not absorb in the emission spectrum of a photometer usually utilizes the formation of a complex of the substance to be measured with a compound that exhibits high absorption in the desired range. For example, B. Wyrwas et al. described in J. Surfact. Deterg. 2014, 17, 191 - 198 the determination of anionic surfactants, such as dodecylbenzenesulfonate, in river water. For this purpose, water containing dodecylbenzenesulfonate is mixed with methylene blue, and the formed complex is extracted into the chloroform phase, which is then examined by spectrophotometry. However, chloroform is classified as a hazardous substance, more precisely toxic when inhaled and suspected of causing cancer and genetic defects. Therefore, an object of the present invention is to provide a method capable of determining an N-acylsarcosine compound of formula (I) without using a hazardous solvent.

[0023] A further aspect of the present invention thus relates to a method for determining the concentration of a compound of formula (I) (in the form of its acid or its salt) in an aqueous solution or emulsion of a compound of formula (I) (or its salt), which method comprises the following steps:

[0024] i) adding a cationic phenothiazine dye to a specified amount of an aqueous solution or emulsion containing a compound of formula (I) or its salt;

[0025] ii) subjecting the mixture of step i) to extraction with a liquid extractant, said liquid extractant comprising at least 95% by weight of the total amount of extractant of a C8-C 10 alkan-ol, in particular 1-nonanol;

[0026] iii) separating the liquid extractant from the aqueous phase; and

[0027] iv) photometrically determining the concentration of the phenothiazine dye in the extractant. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Figure 1 Nyquist plot showing electrochemical impedance measurements of a low-carbon steel electrode in deionized water containing 50 ppm of oleoyl sarcosine (C-1) or cocoyl sarcosine (C-2); or containing 44.7 ppm of oleylamine (CMP-1) (measured by the eosin B method) at pH 9.0 at the 5th measurement point of t = 100 min carried out according to Example 2.

[0030] Figure 2 Figure 2 Calibration curve showing the determination of the concentration of cocoyl sarcosine (Compound C-2) in the absence of chloride ions, which was established according to Example 9 by photometric absorption measurements of the complex formed by methylene blue with five specified concentrations of C-2. The absorption obtained with these five concentrations of C-2 was plotted against the concentration of C-2 [mg / l] and connected by a regression line A. Figure 2 Further shown are calibration curves for the determination of C-2 at five or six specified concentrations in the presence of various specified amounts of chloride ions according to Example 10. The absorption obtained with these five concentrations of C-2 was plotted against the respective C-2 concentration [mg / l] and connected by regression lines B to F, where B is the regression line for conc. Cl - = 31 mg / l; C is the regression line for conc. Cl - = 62 mg / l; D is the regression line for conc. Cl - = 156 mg / l; E is the regression line for conc. Cl - = 218 mg / l; and F is the regression line for conc.​​​​Cl - Regression line of 311 mg / l.

[0031] Figure 3 Figure 3 which is Figure 2 wherein the line segments A to F in C-2 are plotted against the absorption on the y-axis (vertical axis) of the absorption value at conc. = 0 mg / l; and a regression line is drawn. Detailed Description of the Invention

[0033] Definitions

[0034] Unless otherwise specified, the following definitions apply both to the processes of the invention and to the uses of the invention.

[0035] The process for providing corrosion protection is hereinafter generally referred to as the "(process of the) invention", and the process for determining the concentration of the compound of formula (I) is generally referred to as the "(determination process of the) invention".

[0036] If a mixture of different N-acylsarcosine compounds of formula (I) or their salts is used, it is understood that the concentration range of 0.01 to 10 mg / kg (and the preferred ranges specified above, below and in the claims) relates to the total amount of compound (I) and not to the individual compound (I) contained in the mixture.

[0037] For the concentration range, the weight of compound (I) relates to their acid form.

[0038] "Average total concentration" is understood as the time average of the concentration. Further details are given below.

[0039] A straight-chain or branched acyclic hydrocarbon radical having 10 to 24 carbon atoms in the present invention is a straight-chain or branched aliphatic group having 10 to 24 carbon atoms. The aliphatic group may be a saturated alkyl group or an unsaturated alkenyl or alkynyl group. Generally, the unsaturated aliphatic group is an alkenyl group. A straight-chain or branched acyclic hydrocarbon radical having 10 to 24 carbon atoms is thus generally a C 10 -C 24 -alkyl or C 10 -C 24 -alkenyl.

[0040] ​​A C1-C6-alkyl group is a saturated straight-chain or branched-chain aliphatic hydrocarbon group having 1 to 6 carbon atoms. Examples of C1-C6-alkyl groups are methyl, ethyl, propyl, isopropyl, n-butyl, 1-methylpropyl (sec-butyl), 2-methylpropyl (isobutyl), 1,1-dimethylethyl (tert-butyl), pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl or 1-ethyl-2-methylpropyl.

[0041] C 10 -C 11 -alkyl is a saturated straight-chain or branched-chain aliphatic hydrocarbon group having 10 or 11 carbon atoms. C 10 -C 11 -alkyl examples are n-decyl, n-undecyl and their positional isomers, such as 2-propylheptyl and the like. C 12 -C 18 -alkyl is a saturated straight-chain or branched-chain aliphatic hydrocarbon group having 12 to 18 carbon atoms. C 12 -C 18 -alkyl examples are n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl, n-heptadecyl, n-octadecyl and their positional isomers. C 12 -C 20 -alkyl is a saturated straight-chain or branched-chain aliphatic hydrocarbon group having 12 to 20 carbon atoms. C 12 -C 20 -alkyl examples are n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl and their positional isomers. C 10 -C 24 -alkyl is a saturated straight-chain or branched-chain aliphatic hydrocarbon group having 10 to 24 carbon atoms. C 10 -C 24 -alkyl examples are n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, n-heneicosyl, n-docosyl and their positional isomers.

[0042] Strictly speaking, the term "alkenyl" refers to a straight-chain or branched-chain aliphatic hydrocarbon group that is mono-unsaturated (i.e., contains one C-C double bond), where the C-C double bond can be in any position. However, as used in the present invention, the term also encompasses "alkapolyenyl", i.e., a straight-chain or branched-chain aliphatic hydrocarbon group having two or more conjugated or separated, but non-cumulative C-C double bonds.

[0043] C 10 -C 11 -Alkenyl is a straight-chain or branched-chain aliphatic hydrocarbon group having 10 or 11 carbon atoms and one or more, preferably 1, 2 or 3 conjugated or separated, but non-cumulative C-C double bonds. In the strict sense of C 10 -C 11 -alkenyl (having only 1 C-C double bond) examples are 1-decenyl, 2-decenyl, 3-decenyl, 4-decenyl, 5-decenyl, 1-undecenyl, 2-undecenyl, 3-undecenyl, 4-undecenyl, 5-undecenyl and their positional isomers. C 10 -C 11Examples of -alkapolyenyl (i.e., "alkenyl" having two or more, preferably two or three C-C double bonds) are n-dec-1,3-dienyl, n-dec-1,4-dienyl, n-dec-1,5-dienyl, n-dec-1,6-dienyl, n-dec-1,7-dienyl, n-dec-1,8-dienyl, n-dec-1,9-dienyl, n-dec-2,4-dienyl, n-dec-2,5-dienyl, n-dec-2,6-dienyl, n-dec-2,7-dienyl, n-dec-2,8-dienyl, n-dec-2,9-dienyl, n-dec-3,5-dienyl, n-dec-3,6-dienyl, n-dec-3,7-dienyl, n-dec-3,8-dienyl, n-dec-3,9-dienyl, n-dec-4,6-dienyl, n-dec-4,7-dienyl, n-dec-4,8-dienyl, n-dec-4,9-dienyl, n-dec-5,7-dienyl, n-dec-5,8-dienyl, n-dec-5,9-dienyl, n-dec-6,8-dienyl, n-dec-6,9-dienyl, n-dec-7,9-dienyl, n-undec-1,3-dienyl, n-undec-1,4-dienyl, n-undec-1,5-dienyl, n-undec-1,6-dienyl, n-undec-1,7-dienyl, n-undec-1,8-dienyl, n-undec-1,9-dienyl, n-undec-1,10-dienyl, n-undec-2,4-dienyl, n-undec-2,5-dienyl, n-undec-2,6-dienyl, n-undec-2,7-dienyl, n-undec-2,8-dienyl, n-undec-2,9-dienyl, n-undec-2,10-dienyl, n-undec-3,5-dienyl, n-undec-3,6-dienyl, n-undec-3,7-dienyl, n-undec-3,8-dienyl, n-undec-3,9-dienyl, n-undec-3,10-dienyl, n-undec-4,6-dienyl, n-undec-4,7-dienyl, n-undec-4,8-dienyl, n-undec-4,9-dienyl, n-undec-4,10-dienyl, n-undec-5,7-dienyl, n-undec-5,8-dienyl, n-undec-5,9-dienyl, n-undec-5,10-dienyl, n-undec-6,8-dienyl, n-undec-6,9-dienyl, n-undec-6,10-dienyl, n-undec-7,9-dienyl, n-undec-7,10-dienyl, n-undec-8,10-dienyl, n-dec-1,3,5-trienyl, n-dec-1,3,6-trienyl, n-dec-1,3,7-trienyl, n-dec-1,3,8-trienyl, n-dec-1,3,9-trienyl, n-dec-1,4,6-trienyl, n-dec-1,4,7-trienyl, n-dec-1,4,8-trienyl, n-dec-1,4,9-trienyl, n-dec-1,5,7-trienyl, n-dec-1,5,8-trienyl, n-dec-1,5,9-trienyl, n-dec-1,6,8-trienyl, n-deca-1,6,9-trienyl, n-deca-1,7,9-trienyl, n-deca-2,4,6-trienyl, n-deca-2,4,7-trienyl, n-deca-2,4,8-trienyl, n-deca-2,4,9-trienyl, n-deca-2,5,7-trienyl, n-deca-2,5,8-trienyl, n-deca-2,5,9-trienyl, n-deca-2,6,8-trienyl, n-deca-2,6,9-trienyl, n-deca-2,7,9-trienyl, n-deca-3,5,7-trienyl, n-deca-3,5,8-trienyl, n-deca-3,5,9-trienyl, n-deca-3,6,8-trienyl, n-deca-3,6,9-trienyl, n-deca-3,7,9-trienyl, n-deca-4,6,8-trienyl, n-deca-4,6,9-trienyl, n-deca-4,7,9-trienyl, n-deca-5,7,9-trienyl, n-undeca-1,3,5-trienyl, n-undeca-1,3,6-trienyl, n-undeca-1,3,7-trienyl, n-undeca-1,3,8-trienyl, n-undeca-1,3,9-trienyl, n-undeca-1,3,10-trienyl, n-undeca-1,4,6-trienyl, n-undeca-1,4,7-trienyl, n-undeca-1,4,8-trienyl, n-undeca-1,4,9-trienyl, n-undeca-1,4,10-trienyl, n-undeca-1,5,7-trienyl, n-undeca-1,5,8-trienyl, n-undeca-1,5,9-trienyl, n-undeca-1,5,10-trienyl, n-undeca-1,6,8-trienyl, n-undeca-1,6,9-trienyl, n-undeca-1,6,10-trienyl, n-undeca-1,7,9-trienyl, n-undeca-1,7,10-trienyl, n-undeca-1,8,10-trienyl, n-undeca-2,4,6-trienyl, n-undeca-2,4,7-trienyl, n-undeca-2,4,8-trienyl, n-undeca-2,4,9-trienyl, n-undeca-2,4,10-trienyl, n-undeca-2,5,7-trienyl, n-undeca-2,5,8-trienyl, n-undeca-2,5,9-trienyl, n-undeca-2,5,10-trienyl, n-undeca-2,6,8-trienyl, n-undeca-2,6,9-trienyl, n-undeca-2,6,10-trienyl, n-undeca-2,7,9-trienyl, n-undeca-2,7,10-trienyl, n-undeca-2,8,10-trienyl, n-undeca-3,5,7-trienyl, n-undeca-3,5,8-trienyl, n-undeca-3,5,9-trienyl, n-undeca-3,5,10-trienyl, n-undeca-3,6,8-trienyl, n-undeca-3,6,9-trienyl, n-undeca-3,6,10-trienyl, n-undeca-3,7,9-trienyl, n-undeca-3,7,10-trienyl, n-undeca-3,8,10-trienyl, n-undeca-4,6,8-trienyl, n-undeca-4,6,9-trienyl, n-undeca-4,6,10-trienyl, n-undeca-4,7,9-trienyl, n-undeca-4,7,10-trienyl, n-undeca-4,8,10-trienyl, n-undeca-5,7,9-trienyl, n-undeca-5,7,10-trienyl, n-undeca-5,8,10-trienyl and their positional isomers.,

[0044] C 12 -C 18 -alkenyl is a straight-chain or branched-chain aliphatic hydrocarbon group having 12 to 18 carbon atoms and one or more, preferably 1, 2 or 3 conjugated or isolated, but non-cumulative C-C double bonds. In the strict sense, C 12 -C 18 -alkenyl (having only 1 C-C double bond) examples are 1-dodecenyl, 2-dodecenyl, 3-dodecenyl, 4-dodecenyl, 5-dodecenyl, 6-dodecenyl, 1-tridecenyl, 2-tridecenyl, 3-tridecenyl, 4-tridecenyl, 5-tridecenyl, 6-tridecenyl, 1-tetradecenyl, 2-tetradecenyl, 3-tetradecenyl, 4-tetradecenyl, 5-tetradecenyl, 6-tetradecenyl, 7-tetradecenyl, 1-pentadecenyl, 2-pentadecenyl, 3-pentadecenyl, 4-pentadecenyl, 5-pentadecenyl, 6-pentadecenyl, 7-pentadecenyl, 1-hexadecenyl, 2-hexadecenyl, 3-hexadecenyl, 4-hexadecenyl, 5-hexadecenyl, 6-hexadecenyl, 7-hexadecenyl, 8-hexadecenyl, 1-heptadecenyl, 2-heptadecenyl, 3-heptadecenyl, 4-heptadecenyl, 5-heptadecenyl, 6-heptadecenyl, 7-heptadecenyl, 8-heptadecenyl, 1-octadecenyl, 2-octadecenyl, 3-octadecenyl, 4-octadecenyl, 5-octadecenyl, 6-octadecenyl, 7-octadecenyl, 8-octadecenyl and their positional isomers. C 12 -C 20 -alkapolyenyl (i.e., "alkenyl" having 2 or more, preferably 2 or 3 C-C double bonds) some selected examples are n-octa-9,12-dienyl, n-octa-9,12,15-trienyl, etc.

[0045] C 12 -C 20 -alkenyl is a straight-chain or branched-chain aliphatic hydrocarbon group having 12 to 20 carbon atoms and one or more, preferably 1, 2 or 3 conjugated or isolated, but non-cumulative C-C double bonds. In the strict sense, C 12 -C 20Examples of -enyl (having only 1 C-C double bond) are, in addition to those listed for C 12 -C 18 -enyl, 9-octadecenyl, 1-nonadecenyl, 2-nonadecenyl, 3-nonadecenyl, 4-nonadecenyl, 5-nonadecenyl, 6-nonadecenyl, 7-nonadecenyl, 8-nonadecenyl, 9-nonadecenyl, 1-eicosenyl, 2-eicosenyl, 3-eicosenyl, 4-eicosenyl, 5-eicosenyl, 6-eicosenyl, 7-eicosenyl, 8-eicosenyl, 9-eicosenyl and their positional isomers. C 12 -C 20 -alkapolyenyl (i.e., "enyl" having 2 or more, preferably 2 or 3 C-C double bonds) some selected examples are n-octa-9,12-dienyl, n-octa-9,12,15-trienyl, etc.

[0046] C 10 -C 24 -enyl is a straight-chain or branched aliphatic hydrocarbon group having 10 to 24 carbon atoms and one or more, preferably 1, 2 or 3 conjugated or isolated, but non-cumulative C-C double bonds. C 10 -C 24 Examples of -enyl are those listed above for C 10 -C 11 -enyl and C 12 -C 20 -enyl, and in addition tricosanyl, tetracosanyl and their positional isomers.

[0047] The C-C double bonds in enyl can be cis- or trans-substituted. When enyl is derived from natural fatty acids, the C-C double bonds are usually cis.

[0048] C1-C6-hydroxyalkyl is a C1-C6-alkyl as defined above in which one hydrogen atom is replaced by a hydroxyl group. Examples of C1-C6-hydroxyalkyl are hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl, 1-hydroxypropan-1-yl, 1-hydroxypropan-2-yl, 2-hydroxypropan-1-yl, 2-hydroxypropan-2-yl, 3-hydroxypropan-1-yl, 1-hydroxybutan-1-yl, 1-hydroxybutan-2-yl, 1-hydroxybutan-3-yl, 2-hydroxybutan-1-yl, 2-hydroxybutan-2-yl, 2-hydroxybutan-3-yl, 3-hydroxybutan-1-yl, 4-hydroxybutan-1-yl, 1-hydroxy-2-methyl-propan-1-yl, 2-hydroxy-2-methyl-propan-1-yl, 3-hydroxy-2-methyl-propan-1-yl or 2-(hydroxymethyl)-2-methyl-eth-1-yl.

[0049] A C1-C6-alkoxy group is a C1-C6-alkyl group as defined above which is linked via an oxygen atom. Examples of C1-C6-alkoxy groups are methoxy, ethoxy, n-propoxy, 1-methylethoxy (isopropoxy), butoxy, 1-methylpropoxy (sec-butoxy), 2-methylpropoxy (isobutoxy), 1,1-dimethylethoxy (tert-butoxy), pentyloxy, 1-methylbutoxy, 2-methylbutoxy, 3-methylbutoxy, 1,1-dimethylpropoxy, 1,2-dimethylpropoxy, 2,2-dimethylpropoxy, 1-ethylpropoxy, hexyloxy, 1-methylpentyloxy, 2-methylpentyloxy, 3-methylpentyloxy, 4-methylpentyloxy, 1,1-dimethylbutoxy, 1,2-dimethylbutoxy, 1,3-dimethylbutoxy, 2,2-dimethylbutoxy, 2,3-dimethylbutoxy, 3,3-dimethylbutoxy, 1-ethylbutoxy, 2-ethylbutoxy, 1,1,2-trimethylpropoxy, 1,2,2-trimethylpropoxy, 1-ethyl-1-methylpropoxy or 1-ethyl-2-methylpropoxy.

[0050] C8-C 10 -alkanols are straight-chain or branched C8-C 10 -alkyl groups as defined above which are substituted by a hydroxyl group at any position. Examples are n-octanol, n-nonanol, n-decanol, 2-ethylhexanol, neodecanol, 2-propylheptanol, neodecanol and their other positional isomers.

[0051] If mixtures of different compounds I are used, the compounds usually differ in the definition of their R.

[0052] Unless otherwise specified, when the amount or concentration of a component is given as "ppm", this corresponds to 1 g of the component / 1,000,000 g of the reference substance (or 1 mg / kg). If the unit "ppm" is used to specify the concentration of a component in water, taking into account that the density of water is close to 1 g / l, 1 ppm can also be understood as 1 g of the component / 1 cubic meter of water (or 1 mg / l).

[0053] Embodiments of the Invention

[0054] Unless otherwise specified, the following description of the general and preferred embodiments of the present invention relates both to the method of the present invention and to the use of the present invention.

[0055] In a particular embodiment, in the method and use of the present invention, polymaleic acid or its salts (such as those contained in the formulation of JP S57-185988) are not added to the water used or present in a pressurized water-steam system.

[0056] In a particular embodiment, in the processes and uses of the present invention, the product obtained by reacting the sulfonyl chloride of an aromatic, alkylaromatic, aliphatic or cycloaliphatic hydrocarbon having 12 - 24 carbon atoms with ammonia or a primary aliphatic amine and then reacting the resulting sulfonamide with a halogen carboxylic acid having 2 - 9 carbon atoms, and the reaction product of a sulfonyl chloride with an amino carboxylic acid having 2 - 9 carbon atoms in the presence of a base, and salts of these reaction products (component A of DE 1916628) are not added to the water used or present in a pressurized water-steam system.

[0057] In a particular embodiment, in the processes and uses of the present invention, poly(maleic acid) or its salts, and the product obtained by reacting the sulfonyl chloride of an aromatic, alkylaromatic, aliphatic or cycloaliphatic hydrocarbon having 12 - 24 carbon atoms with ammonia or a primary aliphatic amine and then reacting the resulting sulfonamide with a halogen carboxylic acid having 2 - 9 carbon atoms, and the reaction product of a sulfonyl chloride with an amino carboxylic acid having 2 - 9 carbon atoms in the presence of a base, and salts of these reaction products (component A of DE 1916628) are not added to the water used or present in a pressurized water-steam system.

[0058] In another particular embodiment, in the processes and uses of the present invention, N,N'-disubstituted aminomethyltriazole derivatives of the following formula are not added to the water used or present in a pressurized water-steam system:

[0059] T-CH2-NR2

[0060] wherein T is an optionally substituted 1,2,3-benzothiazole group or an optionally substituted 1,2,4-triazole group, and R is a hydroxyalkyl group (component b of EP 1092788 A2).

[0061] In a very particular embodiment, the above poly(maleic acid) or its salts, and the product obtained by reacting the sulfonyl chloride of an aromatic, alkylaromatic, aliphatic or cycloaliphatic hydrocarbon having 12 - 24 carbon atoms with ammonia or a primary aliphatic amine and then reacting the resulting sulfonamide with a halogen carboxylic acid having 2 - 9 carbon atoms, and the reaction product of a sulfonyl chloride with an amino carboxylic acid having 2 - 9 carbon atoms in the presence of a base; or salts of these reaction products; and the above triazole derivatives are not added to the water used or present in a pressurized water-steam system.

[0062] N-acylsarcosine compound (I)

[0063] If mixtures of different compounds I are used, these compounds differ in the definition of their R. Such mixtures can be obtained by mixing different N-acylsarcosines (I) or by subjecting mixtures of different carboxylic acids R-C(=O)OH to amidation with sarcosine or by subjecting mixtures of different carboxylic acids R-C(=O)OH to amidation with methylamine and subsequent reaction of the resulting amide with formaldehyde. Mixtures of different carboxylic acids can be obtained by mixing different carboxylic acids, but are more conveniently obtained by hydrolysis of natural oils or fats. Natural oils and fats are usually mixtures of different triglycerides, where individual triglyceride molecules can be derived from different fatty acids. Hydrolysis of such natural triglycerides and subsequent amidation of the resulting fatty acid mixture with sarcosine will of course give mixtures of compounds I having different groups R.

[0064] Examples of natural oils (vegetable oils) that can be used to derive mixtures of different compounds (I) are sunflower oil, rapeseed oil, soybean oil, coconut oil, palm oil, palm kernel oil, maize oil (corn oil), olive oil, peanut oil, cottonseed oil, linseed oil, sesame oil, safflower oil, etc. An example of a natural fat that can be used to derive mixtures of different compounds (I) is beef tallow fat.

[0065] R in formula (I) is preferably selected from C 12 -C 20 -alkyl and C 12 -C 20 -alkenyl having 1, 2 or 3 C=C double bonds; wherein in the case of using mixtures of different N-acylsarcosine compounds of formula (I), in up to 25% by weight of the N-acylsarcosine compound (I) based on the total weight of the mixture, R can also be C5-C9 alkyl; and in up to 55% by weight of the N-acylsarcosine compound (I) based on the total weight of the mixture, R can also be selected from C 10 -C 11 -alkyl and C 10 -C 11 -alkenyl having 1 C=C double bond.

[0066] Preferably, R in formula (I) has on average 12 to 18 carbon atoms.

[0067] In a particular embodiment, a single compound I (i.e., not a mixture of compounds I) is used, and in such a compound R is preferably C 12 -C 18 -alkyl or C 12 -C 18 -alkenyl having 1 C=C double bond; wherein R is more preferably C 14 -C 18 -alkenyl having 1 C=C double bond, especially C16 -C 18 -alkenyl. In one specific embodiment, R is derived from oleic acid ((9Z)-octadecenoic acid); that is, R is (8Z)-heptadecenyl.

[0068] In another specific embodiment, a mixture of different compounds I in which R has different meanings is used. In such a mixture, R is preferably selected from C 12 -C 20 -alkyl and C 12 -C 20 -alkenyl having 1, 2 or 3 C═C double bonds; wherein in up to 25% by weight of the N-acylsarcosine compound (I) based on the total weight of the mixture, R can also be C5-C9 alkyl; and in up to 55% by weight of the N-acylsarcosine compound (I) based on the total weight of the mixture, R can also be selected from C 10 -C 11 -alkyl and C 10 -C 11 -alkenyl having 1 C═C double bond. In other words, in such a mixture, in at least 20% by weight of the compound I present in the mixture based on the total weight of the mixture, R is preferably selected from C 12 -C 20 -alkyl and C 12 -C 20 -alkenyl having 1, 2 or 3 C═C double bonds.

[0069] Preferably, if a mixture of different compounds (I) is used, the group R-C(═O) in acylsarcosine (I) is derived from natural oils or fats, particularly derived from vegetable oils. Examples of suitable vegetable oils are sunflower oil, rapeseed oil, soybean oil, coconut oil, palm oil, palm kernel oil, maize oil (corn oil), olive oil, peanut oil, cottonseed oil, linseed oil, sesame oil, safflower oil. Among them, preferred are sunflower oil, rapeseed oil, soybean oil, coconut oil, palm oil, palm kernel oil, maize oil (corn oil) and olive oil. A specific example is coconut oil. Thus, a specific example of the mixture of different compounds I is a mixture that can be obtained by hydrolysis of coconut oil and subsequent amidation (formally) of the fatty acids obtained from hydrolysis with sarcosine.

[0070] In the use of the single compound (I) and mixtures of different compounds (I), preference is given to using mixtures of different compounds (I). Among the mixtures of different compounds (I), preference is given to those derived from vegetable oils such as sunflower oil, rapeseed oil, soybean oil, coconut oil, palm oil, palm kernel oil, maize oil (corn oil), olive oil, peanut oil, cottonseed oil, linseed oil, sesame oil or safflower oil, preferably those derived from sunflower oil, rapeseed oil, soybean oil, coconut oil, palm oil, palm kernel oil, maize oil (corn oil) or olive oil, especially those derived from coconut oil, more precisely, mixtures obtainable by hydrolysis of vegetable oils such as sunflower oil, rapeseed oil, soybean oil, coconut oil, palm oil, palm kernel oil, maize oil (corn oil), olive oil, peanut oil, cottonseed oil, linseed oil, sesame oil or safflower oil, preferably sunflower oil, rapeseed oil, soybean oil, coconut oil, palm oil, palm kernel oil, maize oil (corn oil) or olive oil, especially coconut oil and subsequent amidation of the fatty acids obtained from the hydrolysis with sarcosine.

[0071] N-acyl sarcosine compounds (I) are known and commercially available. They can be obtained by methods known in the art, such as amidation of a carboxylic acid R-C(=O)OH or a more reactive derivative thereof, such as a halide, especially a chloride; or an anhydride; or an ester thereof with sarcosine or a salt thereof. Another method is the reaction of an amide R-C(=O)-NHCH3 with formaldehyde to give R-C(=O)-N(CH3)-CH2OH and subsequent carbonylation with CO using a suitable carbonylation catalyst.

[0072] An N-acylsarcosine compound of formula (I), a mixture of different N-acylsarcosine compounds of formula (I), or a salt thereof is added to the water used to operate the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 10 mg / kg, i.e., in the range of 0.01 to 10 mg of all compounds (I) (calculated as the acid form) / kg of the water contained in the water-steam system. In a preferred embodiment, an N-acylsarcosine compound of formula (I), a mixture of different N-acylsarcosine compounds of formula (I), or a salt thereof is added to the water used to operate the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 8 mg / kg, more preferably in the range of 0.02 to 6 mg / kg, especially in the range of 0.02 to 5 mg / kg, more especially in the range of 0.05 to 5 mg / kg, still more especially in the range of 0.1 to 5 mg / kg, such as in the range of 0.5 to 5 mg / kg; in particular in the range of 0.1 to 3.5 mg / kg, more particularly in the range of 0.5 to 3.5 mg / kg, still more particularly in the range of 0.5 to 3 mg / kg, very especially in the range of 0.8 to 2.5 mg / kg.

[0073] As used herein, the term "average total concentration" is understood to be the time-average of the concentration, which means that over the course of the operating time of the water-steam system, the overall concentration of all N-acylsarcosine compounds of formula (I) or their salts in the water used to operate the water-steam system is on average within the above range. In practice, the concentration of the N-acylsarcosine compound of formula (I) or its salts in the water does not necessarily be within the above range at every point in time during the operation of the water-steam system. On the contrary, it is possible for the concentration to be outside the above range for a certain period of time. However, any period during which the concentration of the N-acylsarcosine compound of formula (I) or its salts is outside the above range generally does not exceed 4 hours, especially 2 hours. In addition, during these periods, the concentration generally does not exceed twice the upper limit given above and does not drop to 0 or only briefly (preferably not more than 4 hours).

[0074] The concentrations given above relate to the concentration of the N-acylsarcosine compound of formula (I) or its salts in those components of the water-steam system in which the water used to operate the water-steam system is in the liquid state. Those skilled in the art also understand that the concentration of the N-acylsarcosine compound of formula (I) or its salts in the water used to operate the water-steam system may vary to some extent within the water-steam system and not be the same at every point in the water-steam system. However, this deviation is not very high and the average concentration range given above is generally maintained in any component of the water-steam system in which the water is in the liquid state.

[0075] In order to monitor the concentration of the N-acylsarcosine compounds of formula (I) or their salts and keep it within the above range, the concentration of the N-acylsarcosine compounds of formula (I) or their salts is usually determined regularly or continuously at at least one point of the water-steam system, especially at at least two points of the water-steam system. For example, if the water-steam system is a water-steam circuit, reference is made to point 8.2 of IAPWS Technical Guidance Document 8 16 (2016) and the references cited therein. Suitable points for determining the concentration of the N-acylsarcosine compounds of formula (I) or their salts are especially those points where the water is in the liquid state. Preferred points for controlling the concentration of the N-acylsarcosine compounds of formula (I) or their salts include, for example

[0076] - feed water, i.e. the water fed into the water-steam circuit from the feed tank;

[0077] - condensate and

[0078] - water in the steam drum, i.e. the water contained in the steam generating part of the boiler.

[0079] In order to monitor the actual concentration of the N-acylsarcosine compounds of formula (I) or their salts, samples are usually taken and the concentration of the N-acylsarcosine compounds of formula (I) or their salts in the samples is determined by standard methods for determining the concentration of anionic surfactants, such as, for example, the methods described by S. Chitikela et al. in Analyst, July 1995, 120, 2001-2004 or by B. Wyrwas et al., J. Surfact. Deterg. 2014, 17, 191-198 or the references cited therein. However, preferably, the concentration of the N-acylsarcosine compounds of formula (I) or their salts is determined by the novel determination method of the present invention described in more detail below. Of course, it is also possible to determine the concentration of the N-acylsarcosine compounds of formula (I) or their salts by on-line measurement, for example by passing a part of the water used to operate the water-steam system through a bypass having a flow-through sensor or a flow-through measuring cell, such as the method of B. Wyrwas et al., J. Surfact. Deterg. 2014, 17, 191-198 or a method similar to that of M. Lendi et al., Power Plant Chemistry 2015, 17(1), pages 8-13. In this regard, further reference is made to point 8.4 of IAPWS Technical Guidance Document 8 16 (2016) and the references cited therein.

[0080] Alternatively, the concentration of the N-acylsarcosine compound of formula (I) or their salts can be calculated from the amount added and the total water content of the system. This is a very practical method for systems where the N-acylsarcosine compound of formula (I) or their salts are added only once and for systems where the N-acylsarcosine compound of formula (I) or their salts are added regularly or continuously to compensate for the inherent losses of the system. Such a calculation is possible when the amount of loss can be determined, calculated or estimated.

[0081] To keep the concentration of the N-acylsarcosine compound of formula (I) or their salts within the above range, any consumed N-acylsarcosine compound (I) or its salt is replenished in an amount such that compound (I) is present in the concentration range given above. For this purpose, the N-acylsarcosine compound of formula (I) or its salt is metered into the water used to operate the water-steam system in an amount such that the above concentration is achieved at least during the operation of the water-steam system.

[0082] To maintain an appropriate concentration of the N-acylsarcosine compound of formula (I) or their salts in the water used to operate the water-steam circuit, the compound can be added in portions or continuously. The amount or rate of addition depends, of course, on the concentration of the N-acylsarcosine compound of formula (I) or their salts determined in the control measurement. In the case where the water-steam system has not been operated previously with the N-acylsarcosine compound of formula (I) or its salt, it is preferred that the amount of the N-acylsarcosine compound of formula (I) or its salt initially added results in only a low concentration close to the lower limit given above, and further additions are made to achieve the preferred concentration range. In particular, an initial overdose should be avoided.

[0083] To this end, the N-acylsarcosine compounds of formula (I) or their salts can be added substantially at any point of the water-steam system, in particular at the points where water is present in liquid form. The points suitable for adding N-acylsarcosine compounds are substantially the same as those for filming amines or for other corrosion protection additives and are substantially known to the person skilled in the art; in the case of a water-steam circuit, for example from A. Bursik et al., Power Plant Chemistry 2015, 17(6), pages 342-353 and from IAPWS Technical Guidance Document 8 16(2016), point 8.5 and the references cited therein. Suitable points include any point between the feed water tank and the boiler, such as the inlet of the boiler feed water pump, the deaeration heater (deaerator), in particular the deaerator outlet, the economizer, in particular the inlet of the feed pump of the low-pressure or high-pressure economizer circuit, the condenser and the pipeline leading to the air-cooled condenser, the condensate extraction pump and / or the drum. Although it may be useful to add at least a part of the N-acylsarcosine compounds of formula (I) or their salts to the condensate (in particular at the condensate discharge pump), they may also be added only via the feed water, for example added to the feed water tank of the boiler or the inlet of the feed water pump.

[0084] The inventors have observed that the vapor / water distribution ratio of compound (I) is such that the volatility is high enough to be transferred into the gas phase and subsequently also into the condensate, but leaves a sufficient part and provides protection for this part. In a preferred embodiment, the method and use of the present invention are used to provide corrosion protection for those components of the pressurized water-steam system that are in contact with steam and / or condensate. Due to the favorable vapor / water distribution ratio, this protective effect is also achieved when compound (I) is introduced into the system only via the feed water.

[0085] In one embodiment, the compound of formula (I) or a mixture thereof is added in its acid form to the water used to operate the water-steam system.

[0086] In another embodiment, the compound of formula (I) or a mixture thereof is added in salt form to the water used to operate the water-steam system. Suitable salts are salts having alkali metal cations, such as Li, Na or K salts, as well as ammonium (NH4 + ) or substituted ammonium salts. Preferred are ammonium and substituted ammonium salts. Suitable substituted ammonium cations are of the formula [NHR 1 R 2 R 3 + wherein R 1 、R 2 and R 3 ​Independently of one another, selected from hydrogen, C1-C6-alkyl, C1-C6-hydroxyalkyl, and C1-C6-alkoxy, provided that R 1 , R 2 , and R 3 at least one of which is not hydrogen; or R 1 and R 2 together with N form a 5- to 10-membered monocyclic or bicyclic ring which may contain additional heteroatoms selected from O and N as ring members, and R 3 is selected from hydrogen, C1-C6-alkyl, C1-C6-hydroxyalkyl, and C1-C6-alkoxy. Examples of amines for generating (by addition of H + ) substituted ammonium cations are dimethylamine, trimethylamine, ethylamine, diethylamine, monoethanolamine (= 2-aminoethanol), diethylhydroxylamine, N,N-dimethyl-2-aminoethanol, N,N-diethyl-2-aminoethanol (= diethylethanolamine; DEAE), 2-amino-2-methylpropanol, methoxypropylamine, isopropoxypropylamine, 3-methoxypropylamine, 5-aminopentanol, dimethylaminoethylpropanol, 1,2-diaminoethane, and morpholine. Specific amines are monoethanolamine (= 2-aminoethanol), N,N-dimethyl-2-aminoethanol, N,N-diethyl-2-aminoethanol (= diethylethanolamine), methoxypropylamine, and 2-amino-2-methylpropanol. A specific amine is N,N-diethyl-2-aminoethanol.

[0087] In one specific embodiment, the compound of formula (I) or a mixture thereof is added in its acid form to the water used to operate a water-steam system.

[0088] In another specific embodiment, the compound of formula (I) or a mixture thereof is added in the form of its salt, in particular its ammonium salt or substituted ammonium salt, to the water used to operate a water-steam system.

[0089] In one specific embodiment, the compound of formula (I) (used in acid form or salt form) is added in the form of an aqueous solution or emulsion of the acid form of the compound of formula (I) or its salt to the water used to operate a water-steam system, where the salt is preferably an ammonium salt or substituted ammonium salt. Preferably, the concentration of the compound of formula (I) in the aqueous solution or emulsion is in the range of 0.5 to 10% by weight, calculated as the acid form of the compound of formula (I) and based on the total weight of the aqueous solution or emulsion. Preferably, the aqueous solution or emulsion consists to at least 99.9% of a mixture of the compound of formula (I), water, and optionally ammonia and / or at least one organic amine. If the compound of formula (I) is added at least in part in the form of an ammonium salt or substituted ammonium salt, ammonia and / or said at least one organic amine are present.

[0090] Pressurized water-steam system

[0091] A "pressurized" water-steam system means that the system operates at a pressure above ambient pressure, typically at least 2 bar (0.2 MPa). Preferably, the pressure in the water-steam system during operation is at least 10 bar (1 MPa), especially at least 20 bar (2 MPa), and particularly at least 30 bar (3 MPa). Generally, the pressure is from 2 to 300 bar (0.2 to 30 MPa), preferably from 10 to 200 bar (1 to 20 MPa), more preferably from 20 to 150 bar (2 to 15 MPa), especially from 30 to 100 bar (3 to 10 MPa), for example from 30 to 70 bar (3 to 7 MPa) or from 30 to 50 bar (3 to 5 MPa). However, the pressure in some components of the water-steam system may be lower, such as in the feed water tank or the pretreatment system (if present).

[0092] A water-steam system in the sense of the present invention is any system in which steam is generated and which has an inner surface that is in principle prone to corrosion. The "inner surface" is the surface of the water-steam system that is in contact with the water or steam passing through or circulating in the water-steam system and which is thus in principle subject to conditions that may cause corrosion. Examples of sensitive components in such a system are boilers (= steam generators), steam pipelines, more generally the pipes connecting different components, condensers, coolers, turbines, turbine blades, feed water tanks, deaeration heaters, economizers, flash tanks, pretreatment systems, etc., which are made of or contain ferrous materials and non-ferrous materials that are in principle prone to corrosion, such as steel, aluminum and its alloys or copper and its alloys. The system may be or include a circuit in which steam condenses, circulates back and evaporates again, such as in a steam-water circuit (WSC); or it may be a non-circulating system in which the steam does not recirculate. The water-steam system may be of industrial scale, for example as part of an industrial plant, such as part of a power plant, including fossil fuel power plants such as coal-fired power plants and gas turbine power plants, biogas power plants, nuclear power plants, geothermal units, plants containing heat recovery steam generators (HRSGs) or dilution steam generators, etc.; or it may be of utility size. The water-steam system generally includes at least a steam generator / boiler, such as a drum boiler or a once-through steam generator. An exception may be geothermal plants, which use steam formed by the pressure release of high-pressure water from a geothermal source.

[0093] In a preferred embodiment, the water-steam system is a water-steam circuit. As mentioned above, the water-steam system can be part of a power plant, including fossil fuel power plants such as coal-fired power plants and gas turbine power plants, biogas power plants, nuclear power plants, plants containing heat recovery steam generators (HRSGs) or dilution steam generators, etc. The method of the present invention is applicable not only to devices operating in continuous mode but also to meeting the high requirements of a water-steam circuit that is part of a power plant operating in a cyclic mode. Compared with the continuous mode, the cyclic mode is understood to be discontinuous operation with frequent short downtimes (shutdown periods). In a power plant, the cyclic mode is similarly understood and refers to the operation of a power generation unit at varying load levels (power demand) in response to changes in the system load (demand) requirements, including on / off and low-load changes. The method of the present invention can achieve efficient and economic corrosion protection under these challenging conditions.

[0094] Advantageously, the N-acyl sarcosines (I) and their salts used in the present invention are almost non-toxic. They are thus suitable for water-steam systems directly or indirectly related to the processing of sensitive articles, such as the production, purification, sterilization (including pasteurization), packaging, or storage of food (including food additives, beverages, and animal feed), cosmetics, or pharmaceuticals. Accordingly, in a specific embodiment, the method and use of the present invention contribute to providing corrosion protection to a pressurized water-steam system for generating steam used in the direct or indirect processing of food (including food additives, beverages, and animal feed), cosmetics, or pharmaceuticals.

[0095] "Processing" refers to any step from the production site to the user / consumer of the article, such as the production, purification, sterilization, pasteurization, cleaning, polishing, packaging, storage, and delivery of the article.

[0096] "Direct processing" means that steam comes into direct contact with an article or its components at some step from the production site to the user / consumer. "Indirect processing" means that steam does not come into direct contact with the article or its components. For example, steam comes into direct contact with sensitive articles or their components in extraction, distillation, drying, sterilization or pasteurization processes during the production, purification, polishing, packaging or storage of these products. Indirect contact means that steam does not come into direct contact with the sensitive article or its components, but comes into contact with other articles, materials or surfaces that subsequently come into contact with the article or its components. Examples are the contact of steam with packaging materials or with surfaces, areas, spaces, devices or materials on which, in which or with which sensitive articles or their components are processed, such as in production, purification, sterilization, pasteurization, cleaning, polishing, packaging or storage. Direct or indirect steam contact with sensitive articles or their components occurs, for example, in the cleaning or sterilization of areas, spaces, surfaces, devices or working materials in food, food additive, beverage, feed, cosmetic or pharmaceutical production, such as extraction or distillation processes, high-pressure food preservation, packaging of food, food additives, beverages, feeds, cosmetics or pharmaceuticals, bakeries, dairy plants, factories producing or processing sugar, canneries, breweries, slaughterhouses, production and packaging sites of pharmaceuticals or cosmetics, etc.

[0097] For the purpose of illustration only of direct contact with food, steam comes into direct contact with food, for example, during can sealing, mussel cooking, in meat and poultry processing, such as plucking (of chickens, ducks, geese, turkeys, etc.) or hog bristle removal; during bleaching, thawing or steaming.

[0098] An example of indirect contact is the water-steam circuit used in a paper-making machine for producing paper suitable for contact with food, feed, cosmetics or pharmaceuticals, such as packaging paper. Thus, in a preferred embodiment, the water-steam system is the water-steam circuit used in a paper-making machine, especially for producing paper suitable for contact with food, feed, cosmetics or pharmaceuticals, such as packaging paper. Another example of indirect contact is steam used for the purification and / or sterilization of packaging materials, such as bottles or cans in breweries (e.g., tunnel pasteurizers) or other beverage industries (for fruit juices, soft drinks, mineral waters, syrups, etc.) or canneries.

[0099] In another embodiment, an N-acylsarcosine compound or a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to geothermal power plants, such as dry steam power plants, flash steam power plants or binary cycle power plants, or geothermal heating units, such as production wells, injection wells, heat exchangers, steam separators, above-ground and underground pipelines, etc. of geothermal district heating units. Obviously, after the power generation / heating cycle, it is not desirable to release water containing sensitive components into the environment.

[0100] The N-acylsarcosine compounds or mixtures of different N-acylsarcosine compounds of formula (I) or their salts can be used in combination with substances commonly used in these facilities, such as phosphonic acids, polymer additives or chelating agents. Examples of suitable phosphonic acids are EDTMP [ethylenediaminetetra(methylenephosphonic acid)], ATMP [aminotri(methylenephosphonic acid)], PBTC (phosphonobutane tricarboxylic acid), TDTMP [tetramethylenediaminetetra(methylenephosphonic acid)], HDTMP [hexamethylenediaminetetra(methylenephosphonic acid)], etidronic acid, HEDP (1-hydroxyethylidene-1,1-diphosphonic acid), DMMP (dimethyl methylphosphonate), vinylphosphonic acid, AMP [aminotri(methylenephosphonic acid)], HPAA (2-hydroxyphosphonocarboxylic acid) or CEPA (2-carboxyethylphosphonic acid). Examples of suitable polymer additives are homopolymers, copolymers and terpolymers of acrylic acid, phosphonopolycarboxylic acids, acrylate / acrylamide copolymers, homopolymers, copolymers and terpolymers of acrylamide and its salts, polyethylene glycol, copolymers and terpolymers based on acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), copolymers and terpolymers based on (meth)acrylic acid and allyl ethers, etc.

[0101] The pressure of such a geothermal system can vary between 2 and 60 bar (0.2 to 6 MPa). Depending on the system, the temperature can vary between 55 and 300 °C. The pH value is usually in the range of 4 to 10.

[0102] In another embodiment, the N-acylsarcosine compounds or mixtures of different N-acylsarcosine compounds of formula (I) or their salts are added to a dilution steam generator (DSG). A dilution steam generator is a low-pressure boiler commonly used in ethylene plants, where they deliver dilution steam for the cracking process. In most cases, the water system is a closed loop from the cracking furnace to the oil quench unit, then to the water quench unit, the oil / water separator and the stripper to the DSG and back to the furnace. The challenge in treating the DSG is in many cases the high concentration of C1-C4 carboxylic acids (mainly formic acid and acetic acid). So the main problem is the corrosion protection of the boilers and the dilution steam pipelines.

[0103] Just to avoid any doubt, the N-acylsarcosine compounds, their mixtures and salts are of course suitable for any pressurized water-steam system. The systems specifically mentioned above (the water-steam systems directly or indirectly related to the processing of sensitive articles, geothermal power plants / heating units and DSGs) only highlight the places where the advantages of the N-acylsarcosine compounds, their mixtures and salts are particularly obvious.

[0104] Operating conditions

[0105] As explained above, the system operates at a pressure above the ambient pressure, typically at least 2 bar (0.2 MPa). Preferably, the pressure in the water-steam system during operation is at least 10 bar (1 MPa), especially at least 20 bar (2 MPa), particularly at least 30 bar (3 MPa). Generally, the pressure is from 2 to 300 bar (0.2 to 30 MPa), preferably from 10 to 200 bar (1 to 20 MPa), more preferably from 20 to 150 bar (2 to 15 MPa), particularly from 30 to 100 bar (3 to 10 MPa), for example from 30 to 70 bar (3 to 7 MPa) or from 30 to 50 bar (3 to 5 MPa). However, the pressure in some components of the water-steam system may be lower, such as in the feed water tank or the pretreatment system (if present).

[0106] Preferably, the temperature in the water-steam system during operation is at least 100 °C, preferably from 150 to 570 °C, especially from 200 to 400 °C, particularly from 200 to 350 °C. However, the temperature in some components of the water-steam system may be lower, such as in the condenser, the feed water tank or the pretreatment system (if present).

[0107] During operation of the water-steam system, the pH is preferably at least neutral (i.e., at least pH 7, for example from 7 to 14 or from 7 to 12 or from 7 to 10). The optimal pH level depends on the specific water-steam system, the materials contained therein that come into contact with water or steam, and the mode of operation. Generally, a system operating continuously is less likely to be corroded due to too low or too high a pH compared to a system operating discontinuously (e.g., in a cyclic mode) or during a shutdown period. A system containing aluminum or aluminum alloy components in contact with water or steam usually operates at a lower pH than a steel system; at least in a non-continuous operating mode. However, geothermal power plants or heating units may also operate at a pH below 7, but the pH is preferably at least 4, more preferably at least 5, especially at least 6, more especially at least 7, for example from 4 to 10 or from 5 to 10 or from 6 to 9.5 or from 7 to 9. Thus, generally, the pH in the water-steam system is usually in the range of from 4 to 14, preferably from 5 to 12, more preferably from 6 to 12, for example from 7 to 12 or from 7 to 11 or from 7.5 to 11, or from 8.0 to 10 or from 8.5 to 10. The pH value refers to the value measured at 20 °C.

[0108] In the case of a water-steam system being a water-steam circuit, maintain the pH value of the water as measured at 20 °C in the range of preferably pH 7.5 to 12, more preferably in the range of 8.0 to 11, especially in the range of pH 8.5 to 10, more especially in the range of pH 8.7 to 10, particularly in the range of pH 9.0 to 10, very particularly in the range of pH 9.2 to 10. This is usually achieved by adding a suitable base. Suitable bases are, for example, alkali metal hydroxides, sodium hydroxide, potassium hydroxide or lithium hydroxide, phosphates such as sodium phosphate, ammonia and alkalized amines. Alkalized amines are volatile amines, especially amines NR 1 R 2 R 3 wherein R 1 、R 2 and R 3 are independently of one another selected from hydrogen, C1-C6-alkyl, C1-C6-hydroxyalkyl and C1-C6-alkoxy, with the proviso that at least one of R 1 、R 2 and R 3 is not hydrogen; or R 1 and R 2 together with N form a 5- to 10-membered monocyclic or bicyclic ring which may contain additional heteroatoms selected from O and N as ring members, and R 3 is selected from hydrogen, C1-C6-alkyl, C1-C6-hydroxyalkyl and C1-C6-alkoxy. Examples of suitable amines NR 1 R 2 R 3 are dimethylamine, trimethylamine, ethylamine, diethylamine, monoethanolamine (= 2-aminoethanol), diethylhydroxylamine, N,N-dimethyl-2-aminoethanol, N,N-diethyl-2-aminoethanol (= diethylethanolamine; DEAE), 2-amino-2-methylpropanol, methoxypropylamine, isopropoxypropylamine, 3-methoxypropylamine, 5-aminopentanol, dimethylaminoethylpropanol, 1,2-diaminoethane, morpholine and mixtures thereof. Specific amines are monoethanolamine (= 2-aminoethanol), N,N-dimethyl-2-aminoethanol, N,N-diethyl-2-aminoethanol (= diethylethanolamine), methoxypropylamine and 2-amino-2-methylpropanol. A specific amine is N,N-diethyl-2-aminoethanol.

[0109] During the operation of the water-steam circuit, the pH value of the water used to operate the water-steam circuit is on average within the above range. In fact, the pH value of the water does not necessarily be within the above range at every point in time during the operation of the water-steam circuit. On the contrary, it is possible for the pH value to be outside the above range for a short period of time. However, any period during which the pH level is outside the above range usually does not exceed 1 hour, especially 30 minutes, to avoid increased corrosion. In addition, during these periods, the pH level usually does not deviate from the limits given above by more than 0.2 pH units, especially not more than 0.1 pH unit.

[0110] Those skilled in the art will also understand that the pH level of the water used to operate the water-steam circuit may vary to some extent within the water-steam circuit and is not the same at every point in the water-steam circuit. However, this deviation is not very high, and the above average pH level is usually maintained in any component of the water-steam circuit in which the water is in a liquid state.

[0111] To monitor the pH level of the water used to operate the water-steam circuit and keep it within the above range, the pH level is usually determined regularly or continuously at at least one point in the water-steam circuit, especially at at least two points in the water-steam circuit. Suitable points for determining the pH level are especially those points where the water is in a liquid state. Preferred points for controlling the pH level include, for example

[0112] - feed water, i.e., the water supplied to the water-steam circuit from the feed tank;

[0113] - condensate and

[0114] - water in the steam drum, i.e., the water contained in the steam generating part of the boiler.

[0115] To monitor the actual pH level of the water used to operate the water-steam circuit, a sample can be taken and the pH of the sample can be determined according to the standard procedures described above, for example, according to the procedures described in DIN EN ISO 10253:2012-04 or other methods known in the art. Of course, it is also possible to determine the pH value by online measurement, for example, by passing a portion of the water used to operate the water-steam circuit through a bypass with a flow-through measuring cell equipped with a pH meter.

[0116] The base used to adjust or maintain the desired pH can be added at basically any point in the water-steam circuit, especially at points where the water is in a liquid form. The points suitable for adding the base are those mentioned above for the addition of N-acylsarcosine or its salts and include, for example, the feed water tank, any point between the feed water tank and the boiler, such as the inlet of the boiler feed pump, the deaerating heater (deaerator), especially the outlet of the deaerator, the economizer, especially the inlet of the feed pump of the low-pressure or high-pressure economizer circuit, the condenser and the pipeline leading to the air-cooled condenser, the condensate extraction pump and / or the drum.

[0117] In order to maintain an appropriate pH level of the water used to run the water-steam circuit, additional alkali can be added in portions or continuously. The amount or rate of addition, of course, depends on the pH measurement results.

[0118] In the case where the water-steam system is a water-steam circuit, it has also been found beneficial to keep the conductivity of the water used to run the water-steam circuit at a maximum of 30 μS / cm, especially at a maximum of 20 μS / cm or a maximum of 10 μS / cm. The conductivity values given here refer to the specific conductivity of a sample of the water used to run the water-steam circuit as measured at 22 °C. The conductivity can be determined by a standard procedure as described, for example, in DIN EN 27888:1993-11. It is obvious to a person skilled in the art that in some cases it may not be possible to measure the conductivity at 22 °C. However, it is not necessary to measure the conductivity at 22 °C because a person skilled in the art is familiar with the temperature dependence of conductivity. Therefore, it is possible to measure the conductivity at a temperature different from 22 °C and make an appropriate correction. Modern conductivity meters usually have a temperature compensation device. Usually, the conductivity is measured in samples where the temperature is in the range of 20 to 27 °C to minimize the temperature effect.

[0119] During the operation of the water-steam circuit, the conductivity of the water used to run the water-steam circuit is on average below the above-mentioned limits. In fact, the conductivity of the water does not necessarily have to be below the above-mentioned limits at every point in time during the operation of the water-steam circuit. On the contrary, it is possible for the conductivity to be slightly above the above-mentioned limits for a short period of time. However, any period during which the conductivity is above the above-mentioned limits usually does not exceed 4 hours, especially 2 hours. In addition, during these periods, the conductivity usually does not exceed 50 μS / cm, especially does not exceed 30 μS / cm or 20 μS / cm.

[0120] A person skilled in the art will also understand that the conductivity of the water used to run the water-steam circuit may vary to some extent within the water-steam circuit and not be the same at every point in the water-steam circuit. However, this deviation is not very high and the above-mentioned limits of conductivity are usually maintained in any component of the water-steam circuit where the water is in the liquid state.

[0121] In order to monitor the conductivity of the water used to run the water-steam circuit and keep it within the above-mentioned range, the conductivity is usually determined regularly or continuously at at least one point in the water-steam circuit, especially at at least two points in the water-steam circuit. Suitable points for determining the conductivity of the water used to run the water-steam circuit are those points where the water is in the liquid state. Preferred points for controlling the pH level include, for example

[0122] - Feed water, i.e., the water fed into the water-steam circuit from the feed tank;

[0123] - Condensate and

[0124] - The water in the steam drum, i.e., the water contained in the steam generating part of the boiler.

[0125] In order to monitor the actual conductivity of the water used to operate the water-steam circuit, a sample can be taken and the conductivity of the sample can be determined according to standard procedures, for example, according to the procedures described in DIN EN 27888:1993-11. Of course, it is also possible to determine the conductivity value by on-line measurement, for example, by passing a part of the water used to operate the water-steam circuit through a bypass with a flow-through measuring cell equipped with a conductivity meter.

[0126] In order to keep the conductivity below the above limits, it may be necessary to remove the ions causing the conductivity from the water. For this purpose, the water circulating in the water-steam circuit can be conducted through a bed of ion exchange resins, especially a mixed bed of cation exchange resins and anion exchange resins, to remove any ionic impurities. These units are also called water polishing units. It is preferred to conduct the condensate through the water polishing unit.

[0127] The N-acylsarcosine compound (I) can be used to provide corrosion protection for various metals, especially ferrous materials and their alloys (such as various steel types), as well as non-ferrous metals and alloys, such as copper, copper alloys, aluminum or aluminum alloys.

[0128] Steam generators and turbines are usually made of ferrous materials, usually steel, while other components, such as condensers or coolers and pipes, as well as other water / steam systems, may be made of or contain non-ferrous materials, such as copper, copper alloys, aluminum or aluminum alloys.

[0129] The type of steel or non-ferrous metal / alloy depends on the type of component and its construction requirements. The steel types commonly used for constructing components of the water-steam circuit can be high-alloy steels or low-alloy steels, including but not limited to, for example, martensitic steels, especially martensitic steels with a chromium content of 9-14%, such as martensitic steels T / P92 and VM12 / VM12-SHC, austenitic steels and ferritic steels, such as low-alloy ferritic steels, such as T / P24, and also nickel-based alloys.

[0130] Typical aluminum materials especially include pure aluminum with an aluminum content > 99% and aluminum alloys, such as aluminum-magnesium alloys, aluminum-magnesium-silicon alloys and aluminum-zinc alloys.

[0131] Typical copper materials include pure copper and brass.

[0132] In particular, the N-acylsarcosine compound (I) can be used to provide corrosion protection for steel, copper and their alloys, especially for steel and copper, especially for steel.

[0133] In addition to compound (I) or its salts and the optional bases described above regarding the salts of compound (I) and regarding pH adjustment, other additives can be added to the water in the steam - water system. These include polymeric additives as dispersants or scale inhibitors or deoxygenating agents.

[0134] Examples of polymeric additives are homopolymers, copolymers and terpolymers of (meth)acrylic acid or higher - order polymers, such as polyacrylic acid, polymethacrylic acid, copolymers and terpolymers of (meth)acrylic acid and (meth)acrylic esters or higher - order polymers, copolymers and terpolymers of acrylic acid and 2 - acrylamido - 2 - methylpropanesulfonic acid (AMPS) or higher - order polymers, and copolymers and terpolymers of (meth)acrylic acid and allyl ethers or higher - order polymers; homopolymers, copolymers and terpolymers of (meth)acrylates different from those mentioned above, such as copolymers and terpolymers of acrylates and acrylamides or higher - order polymers, homopolymers, copolymers and terpolymers of acrylamides different from those mentioned above, phosphonopolycarboxylic acids and polyethylene glycols.

[0135] Examples of deoxygenating agents are hydrazine, carbohydrazide, diethylhydroxylamine, ascorbic acid and its salts, sulfites and bisulfites.

[0136] The present invention also relates to a method for determining the concentration of a compound of formula (I) in an aqueous solution or emulsion of a compound of formula (I), which comprises the following steps:

[0137] i) adding a cationic phenothiazine dye to a specified amount of an aqueous solution or emulsion containing a compound of formula (I) or its salt;

[0138] ii) subjecting the mixture of step i) to extraction with a liquid extractant, said liquid extractant comprising at least 95% by weight of C8 - C 10 alkanols, especially 1 - nonanol;

[0139] iii) separating the liquid extractant from the aqueous phase; and

[0140] iv) photometrically determining the concentration of the phenothiazine dye in the extractant.

[0141] The determination method is based on the fact that when the compound of formula (I) is present in salt form, it forms an ion - association complex (complex) with the (cationic) phenothiazine dye. These complexes are in C8 - C 10It has better solubility in alkanols than in water, so it can be extracted into the organic phase formed by these solvents. Then the absorption of this complex is determined photometrically, more precisely the absorption of its phenothiazine dye moiety. Absorption is a measure of the dye concentration. By continuously measuring the absorbance of the complex formed by the compound of formula (I) of a specified concentration and the phenothiazine dye, a calibration curve can be prepared, which can subsequently correlate the absorption with the concentration of the phenothiazine dye and ultimately with the concentration of compound (I).

[0142] Compound (I) is a weak acid with a pK a roughly in the range of 3 to 5, so buffer systems can be formed in water with their corresponding anions. They mainly exist in the form of salts only when far beyond the pH range in which they form buffer systems. This is usually the case when the pH exceeds 9. However, if a complex is formed with the phenothiazine dye and extracted into the organic phase, this causes the acid / salt equilibrium to shift towards the salt even at significantly lower pH values. Therefore, it is observed that a pH of 6 or even lower is sufficient to cause the acid / salt equilibrium in steps i) and ii) to shift to some extent towards the salt so that compound (I) can be extracted almost completely into the organic phase in the form of a phenothiazine dye association complex. Therefore, before, during or shortly after step i), and in any case before step ii), if the pH of the aqueous solution or emulsion containing the compound of formula (I) is lower than this value, the aqueous solution or emulsion containing the compound of formula (I) is adjusted to a pH of preferably at least 6. More preferably, if the pH of the aqueous solution or emulsion is lower than this limit, the aqueous solution or emulsion containing the compound of formula (I) is adjusted to a pH of at least 6.5. Preferably, the pH adjustment is carried out before adding the phenothiazine dye. Preferably, the aqueous solution or emulsion is adjusted to a pH of 6.5 to 7.5, especially 6.9 to 7.1, particularly 7.0, as measured at 20 °C.

[0143] If the pH of the aqueous solution or emulsion containing the compound of formula (I) or its salt is in the alkaline range from the beginning, usually no pH adjustment is necessary. For safety or any other reasons, it may still be desirable to carry out the measurement near neutral pH. Therefore, in this case, the aqueous solution or emulsion can also be adjusted to a pH of 6.5 to 7.5, especially 6.9 to 7.1, particularly 7.0, as measured at 20 °C.

[0144] Although pH adjustment can in principle be carried out with any water-miscible base (if the starting aqueous solution or emulsion has a pH in the acidic range) or water-miscible acid (if the starting aqueous solution or emulsion has a pH in the basic range), it is preferred to use a buffer. Suitable buffers are all those that have good buffering capacity around neutral pH, such as phosphate buffers, bicarbonate buffers or phosphate / citric acid buffers. Particular use is made of phosphate buffers, such as buffers containing dihydrogen phosphate and hydrogen phosphate, such as potassium dihydrogen phosphate and dipotassium hydrogen phosphate, or sodium dihydrogen phosphate and disodium hydrogen phosphate, or dihydrogen phosphate and hydrogen phosphate of potassium and sodium, such as potassium dihydrogen phosphate and sodium hydrogen phosphate.

[0145] The base, acid or buffer is usually added in the form of an aqueous solution.

[0146] Preferably, regardless of whether the pH is within the desired range, a buffer is added to the sample to be measured.

[0147] Suitable phenothiazine dyes are methylene blue (N,N,N′,N′-tetramethylthioninium chloride), new methylene blue (3,7-bis(ethylamino)-2,8-dimethylphenothiazin-5-ium chloride) and toluidine blue (N′,N′,2-trimethylphenothiazine-3,7-diaminochloride). Methylene blue is preferably used.

[0148] Preferably, the concentration of the phenothiazine dye used in step i) is such that its (molar) amount is equal to or exceeds the maximum (molar) amount of compound (I) expected in the water sample (i.e., the aqueous solution or emulsion containing the compound of formula (I) or its salt). Preferably, the amount of the phenothiazine dye added in step i) exceeds the maximum (molar) amount of compound (I) expected in the water sample. More preferably, relative to 1 mole of compound (I) expected in the water sample, the phenothiazine dye is used in a molar excess of at least 1.05, more preferably in a molar excess of at least 1.1, especially in a molar excess of at least 1.5. The amount of the phenothiazine dye can far exceed the amount of compound (I) without disturbing the assay method. However, for practical reasons, the molar excess is usually not higher than 300 or 200 times the molar amount of compound (I) expected in the water sample. In particular, in step i), the phenothiazine dye is added in an amount of 1.05 to 200 (molar) times, more particularly 1.1 to 150 (molar) times, especially 3 to 100 (molar) times the maximum amount of compound (I) expected in the water sample. The maximum amount of compound (I) expected in the water sample can be easily calculated or estimated from the amount added to the system and the amount of water present in the system. In the case where the added amount is unknown, an approximate amount can be determined by preliminary tests.

[0149] The phenothiazine dye is usually added as an aqueous solution.

[0150] If a predetermined amount of the phenothiazine dye solution and the buffer solution has been used, determine or calculate the final volume of the aqueous solution (containing compound (I), the phenothiazine dye and, if present, a base or preferably a buffer) obtained before carrying out step ii).

[0151] In step i), the temperature should generally not exceed 70 °C. Preferably, the temperature is from 15 to 35 °C, especially from 20 to 25 °C.

[0152] The extractant for step ii) contains at least 95% by weight of C8-C 10 alkanols, based on the total weight of the extractant.

[0153] Among the C8-C 10 alkanols suitable as liquid extractants, 1-nonanol is preferred.

[0154] The extraction can be carried out once or several times, for example 1, 2 or 3 times, but usually, a single extraction is sufficient. Thus, in one specific embodiment, the aqueous phase is extracted with the alkanol only once.

[0155] C8-C 10 The amount of the C8-C alkanol used is such that the volume ratio of the water sample to the alkanol is preferably from 3:1 to 1:3, more preferably from 2:1 to 1:2, especially from 1.5:1 to 1:1.5, in particular from 1.5:1 to 1.1:1. This amount relates to a single extraction step. In the case of multiple extractions, the total amount of the alkanol used for extraction is generally higher. In this case, it is advantageous to concentrate the organic phase obtained after phase separation, for example by removing a part of the alkanol, for example by distillation, if necessary under reduced pressure.

[0156] In any case, the amount of the alkanol used is a specified amount.

[0157] The extraction is generally carried out by bringing the alkanol into intimate contact with the aqueous phase, for example by vigorous shaking or mixing for a minimum time, for example at least 5 seconds or preferably at least 10 seconds, for example from 5 seconds to 1 minute, or preferably from 10 to 40 seconds.

[0158] The phase separation of the organic phase and the aqueous phase (step iii) can be carried out by conventional means, for example by means of a separating funnel or by removing a part (the upper layer) of the organic phase with a pipette or a syringe.

[0159] In step iii), then a photometric determination of the concentration of the phenothiazine in the complex formed by the phenothiazine dye and compound (I) is carried out on a specified amount of the organic phase. Then the concentration of compound (I) can be determined from its concentration.

[0160] The concentration of phenothiazine can be determined by absorbance measurement in a photometer. Suitable photometers are well-known. As a specific example, mention may be made of the Spektralphotometer DR3900 from Hach Lange GmbH, Germany.

[0161] In a typical photometer, a constant standard light source emits light, which passes through a cuvette containing a liquid sample. Depending on the concentration of the light-absorbing substance in the sample, a portion of the light is absorbed, and the transmitted light is measured with a photocell. By comparison with a calibration curve or table prepared in advance with a series of substances at specified concentrations (determined under defined conditions that strictly correspond to those employed in the examination of the sample of unknown concentration), the transmitted light can be correlated with the concentration of the light-absorbing substance.

[0162] The determination of the concentration of the phenothiazine dye in the organic phase is based on Lambert-Beer's law. Absorbance (which may alternatively be expressed as extinction) is defined by the following equation:

[0163] A λ =ε λ ·c·d

[0164] where

[0165] A λ is the absorbance at a specific wavelength λ;

[0166] ε λ is the spectral extinction coefficient at the same wavelength λ;

[0167] c is the concentration of the light-absorbing substance (here the phenothiazine dye), for example in mol / m 3 ; and d is the optical path length of the cuvette containing the solution of the light-absorbing substance, for example in m.

[0168] The concentration can thus be calculated by solving the equation for c:

[0169] c=A λ / (ε λ ·d)

[0170] The extinction coefficient is substance-specific and also depends on the solvent, pH, and emission wavelength. Specific conditions must therefore be determined by extinction measurements at a given concentration of the substance to be measured in a given solvent at a given pH and a given path length.

[0171] Absorbance is determined as the logarithm (base 10) of the ratio of the intensity of the incident (emitted) light to the intensity of the transmitted light:

[0172] A=log 10 (I0 / I t )

[0173] where

[0174] I0 is the intensity of the irradiation light, for example in W / m 2 count; and

[0175] I t is the intensity of the transmitted light, for example in W / m 2 count.

[0176] The wavelength λ of the emitted light must of course be within the absorption range of the phenothiazine dye used. Generally, λ is in the range of 550 to 700 nm, preferably 600 to 680 nm, particularly 610 to 660 nm, for example 610 nm or 650 nm or 660 nm. In a specific embodiment, light with λ of 660 nm is used.

[0177] The absorption or extinction generally should not exceed 1.6. If an absorption >1 is observed, it is recommended to dilute the water sample with a specified amount of water before, during or after step i), and in any case before step ii).

[0178] The sample for photometric determination in step iii) has a temperature of 10 to 35 °C, preferably 15 to 30 °C, particularly 20 to 25 °C.

[0179] In practice, the concentration of compound (I) is determined by comparing the absorption with an absorption calibration curve established by measuring a solution of compound (I) with a determined concentration. Since the absorption depends not only on the concentration of the test compound, but also on other factors such as the specific compound used, the dye forming a complex with the compound, the extractant, the pH of the initial solution, the wavelength of the emitted light, the path length of the light passing through the sample (and thus the size of the cuvette), and the photometer used, the calibration curve must be established under the same conditions as the test for determining the unknown concentration of compound (I) to obtain reliable results. The calibration curve for a specific compound (I) or its specific mixture must be established by measuring the absorption of the specific compound I (mixture)-dye complex within the specified concentration range of compound I (mixture). If the calibration curve [absorption vs concentration of compound I (mixture)] shows that the correlation between absorption and concentration is linear, the concentration can be more easily determined by mathematical calculation: in the case of a linear correlation between absorption and concentration, the absorption value (y-axis) can be plotted against the corresponding concentration of compound (I) used for calibration (x-axis) in a graph to obtain a (regression) line with a slope "a" and a y-intercept (x = 0) "b". b is determined experimentally (absorption when there is no compound (I) but all other components are present) or by extrapolating the regression line to x = 0. The absorption can be expressed as the product of the slope and the concentration plus the y-intercept:

[0180] Absorbance = a × conc.(Compound I) + b (1)

[0181] Solving the equation for the concentration gives the following equation, from which the concentration of the tested Compound (I) can be calculated by measuring the absorbance (under the same conditions as for calibration):

[0182] conc.(Compound I) = (Absorbance - b) : a (2)

[0183] It has been found that for Compound (I), the correlation between absorbance and concentration is linear at least between 0.1 and 2 mg / l, which is the relevant range for determining the concentration of Compound (I). In cases of higher concentrations where this correlation is no longer linear or its linearity is unknown, if necessary, the sample can be diluted by a specified factor to reach a concentration at which linearity is obtained. Otherwise, the resulting absorbance is correlated with the concentration simply by comparison with the calibration curve.

[0184] It has been found that higher concentrations of chloride ions can distort the determination of the concentration of Compound (I). Therefore, if the sample contains chlorides at a concentration exceeding 30 mg / l, the chloride concentration must be determined and the absorbance result must be adjusted. The chloride concentration can be determined by common means, such as by titration (e.g., various argentometric titrations) or using a commercial kit, such as test strips from Hach Lange GmbH, Germany, which are capable of determining chloride concentrations in the range of 30 to 300 mg / l. To adjust the absorbance result, for example, a calibration curve of various specified chloride concentrations is established by measuring the absorbance of the chloride - dye complex within the specified concentration range of chlorides. If the calibration curve (absorbance vs chloride concentration) shows that the correlation between absorbance and concentration is linear, the absorbance values (y - axis) can be plotted against the corresponding chloride concentrations (x - axis) used for calibration in a graph to obtain the (regression) line with slope "d" and ordinate intercept (x = 0) "b". b is determined experimentally (absorbance when there is no Compound (I) but all other components are present) or by extrapolating the regression line to x = 0. Theoretically, b should be the same as b in Equation (1) or 2 in this case. The absorbance can be expressed as the product of the slope and the concentration plus the ordinate intercept:

[0185] Absorbance = d × conc.(Chloride) + b (3)

[0186] Solving the equation for the concentration gives the following equation (4):

[0187] conc.(Chloride) = (Absorbance - b) : d (4)

[0188] Combining Equation (2) and (4) gives Equation (5), which enables the determination of the concentration of Compound (I) taking into account the interference of chloride ions:

[0189] conc. (Compound I) = (Absorbance - d × conc. (Chloride) - b) : a (5)

[0190] Outside the linear range, calibration curves of different concentrations of Compound (I) in the presence of different concentrations of chloride ions must be used.

[0191] It has also been found that higher concentrations of bicarbonate ions may distort the determination of the concentration of Compound (I). Therefore, if the sample contains bicarbonate at a concentration exceeding 1.4 mmol / l, the bicarbonate concentration must be determined and the absorbance results must be adjusted. The bicarbonate concentration can be determined by common means, such as by titration or using commercial test kits, such as test strips from Hach Lange GmbH, Germany or Macherey Nagel GmbH & Co. KG, Germany. Considering that most test strips are customized for the determination of calcium carbonate, for practical reasons, the bicarbonate concentration is determined as calcium carbonate, which can be calculated back to the bicarbonate content based on the pH of the sample. The test strips are capable of determining carbonate concentrations in the range of 0 to 240 mg / l. To adjust the absorbance results, calibration curves of various specified carbonate concentrations are established, for example, by measuring the absorbance of the carbonate-dye complex within the specified concentration range of carbonate.

[0192] If the calibration curve (Absorbance vs. Concentration of carbonate) shows that the correlation between absorbance and concentration is linear, the absorbance values (y-axis) can be plotted against the corresponding concentrations of carbonate used for calibration (x-axis) in a graph to obtain the (regression) line with slope "d" and ordinate intercept (x = 0) "b". b is determined experimentally (absorbance when there is no Compound (I) but all other components are present) or by extrapolating the regression line to x = 0. As described above for chloride, the absorbance can be expressed as the product of the slope and the concentration plus the ordinate intercept.

[0193] However, in most applications, bicarbonate anions almost never occur in the absence of chloride ions. Therefore, the determination of the concentration of Compound (I) must take into account both of these interfering species. The absorbance in this case is thus represented as a linear combination of three lines.

[0194] Outside the linear range, calibration curves of different concentrations of Compound (I) in the presence of different concentrations of bicarbonate and chloride ions must be used.

[0195] It is also possible to apply this determination method to on-line measurement, for example, by passing a part of the water used to operate the water-steam system through a bypass with a flow-through sensor or a flow-through measurement cell, for example, by a method similar to that of B. Wyrwas et al., J. Surfact. Deterg. 2014, 17, 191-198 or a method similar to that of M. Lendi et al., Power Plant Chemistry 2015, 17(1), pages 8-13.

[0196] This determination method is applicable to samples of the compound of formula (I) [aqueous solution or emulsion of the compound of formula (I)] containing the compound of formula (I) at a total concentration of at least 0.01 mg / kg, preferably at least 0.05 mg / kg, more preferably at least 0.1 mg / kg (calculated as the acid form of the compound of formula (I) and based on the total weight of the aqueous solution or emulsion). This method performs well at a total concentration of up to 2 mg / kg or even slightly higher. In the case of higher concentrations, for example, if the absorption is higher than 1.6, it is recommended to dilute the sample in the specified manner.

[0197] This method uses a relatively harmless C8-C 10 alkanol as the extractant and avoids the significantly more dangerous chloroform used in the prior art methods for determining the concentration of anionic surfactants such as dodecylbenzenesulfonate.

[0198] The present invention is illustrated in more detail in the following examples and drawings. Examples

[0199] Products and equipment used

[0200] The following products were used in the test procedure:

[0201] C-1: Crodasinic TM O: Oleoyl sarcosine; from Croda

[0202] C-2: Crodasinic TM C: Cocoyl sarcosine; sarcosine amide of the fatty acids of coconut oil; from Croda

[0203] Cmp-1: OD: Oleylamine; from Nouryon

[0204] Cmp-2 O: Oleyldipropylenetriamine; from Nouryon

[0205] P-1: A composition containing 2.0% by weight of C-1, 27.0% by weight of diethylethanolamine and 71% by weight of deionized water

[0206] P-2: Composition containing 2.0 wt% C-2, 27.0 wt% diethylethanolamine and 71 wt% deionized water

[0207] Cmp-P-1: a composition containing 2.0 wt% Cmp-1, 27.0 wt% diethylethanolamine, 0.6 wt% octanoic acid and 70.4 wt% deionized water

[0208] Note: Cmp-P-1 contains caprylic acid for stabilization. This is not required for P-1 and P-2.

[0209] The following pilot boiler system was used:

[0210] The 1.5 l natural circulation pilot boiler was configured to be able to take samples from the steam as well as from the water phase during the entire test.

[0211] It must be noted that in a pressurized water-steam system at an industrial scale, the concentrations required are significantly lower than those used in the pilot boiler experiments below. One reason for this is that the residence time, i.e. the time it takes for the steam to pass completely through a specified section of the system once, is typically longer in an industrial system than in the pilot boiler.

[0212] As an example, the residence time in a triple pressure CCGT (combined cycle gas turbine) power plant is compared with a currently used pilot boiler:

[0213] Table 1a

[0214]

[0215] HP = High Pressure; LP = Low Pressure

[0216] As can be seen, the residence time in the pilot boiler is significantly shorter. Shorter residence time means that the N-acylsarcosines have less time to exert their anti-corrosion effect, so higher concentrations are required to achieve the same effect as in a system with a longer residence time.

[0217] Furthermore, in many industrial-scale plants, the corrosion inhibitor is metered in continuously or periodically. This also reduces the concentration required to obtain the desired degree of corrosion protection compared to a pilot boiler, where the corrosion inhibitor is metered in once at the start of the experiment.

[0218] Example 1: Determination of distribution ratio

[0219] The distribution ratio (DR) shows how a substance partitions between the water phase and the vapor phase. Values above 1 indicate that the concentration accumulated in the vapor phase is higher than in the water phase, while values < 1 indicate that the concentration of the substance in water is higher than in vapor.

[0220] The distribution ratio is calculated as follows:

[0221] DR (Distribution Ratio) = c (substance in steam) : c (substance in water)

[0222] The distribution ratio was determined in a pilot boiler system at 20 - 60 bar (2 - 6 MPa) (213 - 277 °C). The concentration of each substance was determined by a colorimetric test using a cuvette from Hach Lange GmbH, Germany (LCK314) as the COD value (chemical oxygen demand) in mg O2 / l.

[0223] 1.5 liters of ultrapure water (18.2 mΩ) was filled into the boiler. With all valves closed, the stirring speed was set to 150 rpm and the internal temperature was set to 60 °C. The entire system was purged with nitrogen at approximately 5 bar (0.5 MPa). After maintaining at 60 °C for 15 minutes, 300 mg of the material to be tested (concentration in the boiler: 200 mg / l) was added. Then the internal temperature was set to 213 °C. After the set temperature and pressure had been constant for at least 6 hours, a sample was taken. Then the internal temperature was set to 252 °C. After the set temperature and pressure had been constant for at least 6 hours, a sample was taken. Then the internal temperature was set to 276 °C. After the set temperature and pressure had been constant for at least 6 hours, a sample was taken. The concentration of each substance was determined by a colorimetric test using a cuvette from Hach Lange GmbH, Germany (LCK314) as the COD value (chemical oxygen demand) in mg O2 / l. The results are compiled in Tables 1b, 2, and 3.

[0224] Table 1b: Distribution Ratio of C-1 (Oleoyl Sarcosine; 200 mg / l)

[0225]

[0226] Table 2: Distribution Ratio of C-2 (Cocoyl Sarcosine; 200 mg / l)

[0227]

[0228] Table 3: Distribution Ratio of Cmp-1 (Oleylamine; 200 mg / l)

[0229]

[0230] It can be seen that C-1 and C-2 have distribution ratios suitable for the desired purpose and comparable to Cmp-1.

[0231] In these experiments, the use concentration of N-acyl sarcosine (and oleylamine) was higher than the concentration provided for the method of the present invention. A higher concentration enables a more precise analysis of the partition ratio compared to a lower concentration, where the influence of measurement error is greater. The purpose of these experiments was only to show that the water / vapor partition of this N-acyl sarcosine is similar to that of the existing oleylamine. The same (relative) behavior can be expected when using a lower concentration.

[0232] Example 2: Corrosion of non-formulated products C-1, C-2, and Cmp-1 measured by electrochemical impedance spectroscopy (EIS) Inhibition

[0233] EIS measurements were used as a method to show the anti-corrosion protection behavior of the test compounds.

[0234] For the electrochemical impedance measurements, the following equipment was used

[0235] - Rotating disk Hach EDI 101 with a speed control unit CTV101 (500 rpm);

[0236] - Potentiostat Autolab PG Stat 12 controlled by Nova 1.11 software (Methrom);

[0237] - Working electrode: Originalys low-carbon steel electrode tip with a diameter of 5 mm and a tip area of 0.196 cm 2 of the end area

[0238] - Counter electrode: Radiometer platinum;

[0239] - Originalys Ag / AgCl reference electrode;

[0240] - 600 mL beaker;

[0241] - Hot plate;

[0242] - pH meter Knick Portamess with a temperature compensation unit and SE102N electrode;

[0243] - Pt 100 thermometer for temperature control at the start and end of the experiment.

[0244] The working electrode was prepared by grinding the low-carbon steel electrode tip at 150 rpm using a grinding machine and silicon carbide grinding papers with grit sizes of P1200, P2500, and P4000 until a flat surface was obtained.

[0245] Dissolve 0.2 g of NaCl in 1 L of ultrapure water (18.2 MΩ) in a beaker. Add the substances to be tested (C-1, C-2, and Cmp-1) to obtain a concentration of 50 mg / l. Set the pH to 9.0 (+ / -0.05) with ammonia (1% dilution). Perform EIS measurements as described below.

[0246] EIS measurement

[0247] Fill 400 ml of test water into a 600 ml beaker. Place the rotating disk working electrode with a low-carbon steel electrode tip, the Pt reference electrode, and the Ag / AgCl reference electrode in the solution as follows: Starting from the middle electrode tip: Place the counter electrode 0.03 cm to the left and the reference electrode 4.5 cm to the right. Place the electrode tip about 90% deep into the solution and place the other electrodes at approximately the same height in the solution.

[0248] Start the test within 2 minutes after the electrode tip has been polished to avoid any oxidation on the surface and to ensure the reproducibility of the test. Start the speed control unit of the rotating disk at a rotational speed of 500 rpm.

[0249] Start the measurement with the open circuit potential (OCP). To do this, measure the voltage of the working electrode relative to the reference electrode to set the starting potential for the actual measurement. Perform the actual potentiostatic measurement by frequency scanning with a frequency response analyzer (FRA). All key parameters of the OCP and FRA are mentioned below. Test - parameters:

[0250] - Current range: 1 mA,

[0251] - OCP determination, up to 120 s,

[0252] - Detection limit: 10 -6 ,

[0253] - Amplitude: 0.01,

[0254] - Logarithmic,

[0255] - Frequency: 65000 Hz to 0.005 Hz (72 frequencies in total),

[0256] - Integration time: 0.125 s,

[0257] - Auto current range: 100 nA to 100 mA,

[0258] - Waveform: Single sine.

[0259] Perform 5 measurements, once every 20 minutes (from 0 minutes to 100 minutes).

[0260] From the observed parameters (frequency ω, excitation signal Et , Response signal I t and the phase shift Ф), the impedance Z(Ф) is calculated, which is a complex number with a real part Z’ and an imaginary part Z”, and they are shown as a Nyquist plot: -Z″ vs Z′ or a Bode plot. Further refer to C. et al., Power Plant Chemistry 2014, 16(5), pp. 284 - 292, especially refer to equations (1) to (4) on page 364. The evaluation of the data can be carried out graphically, or by Nova software or Excel calculation. The measurement results are converted with a metal surface value of 0.196 cm 2 to obtain the actual results in Z″ vs Z′ (Ω·cm 2 ). From the Nyquist plot, the polarization resistance R p can be obtained from the intercepts of the Nyquist plot with the X-axis at low frequency Z’(ω→0) and at high frequency Z’(ω→∞) according to the following equation R p = Z’(ω→0) - Z’(ω→∞). The possible fitting for determining the polarization resistance R p is carried out by Nova software. The higher the polarization resistance R p , the better the corrosion resistance. For practical reasons, it is sufficient to calculate the polarization resistance R p by the following equation:

[0261] R p = Z’(ω = 0.32 Hz) - Z’(ω = 63 kHz).

[0262] The measured Nyquist plot at t = 100 minutes is shown in Figure 1 . These results represent the results obtained at 4 other measurement points, and they all show similar behavior. To interpret this figure, it must be pointed out that in the Nyquist plot, the larger the ΔZ (Ohm·cm 2 )(->x-axis) from left to right, the better the corrosion protection for low-carbon steel.

[0263] As shown in this figure, Compounds C-1 and C-2 show better corrosion inhibition than Cmp-1.

[0264] Example 3: Corrosion test of non-formulated products C-1, C-2, and Cmp-1 on the surface of carbon steel at 252 °C (40 bar; 4 MPa) Fe [mg / l]

[0265] Two 16.6 cm 2Low-carbon steel C1010 specimens (steel St 37) were suspended in the vapor phase of a pilot boiler. The substance to be tested was added to 1.7 liters of ultrapure water (18.2 mΩ) to obtain concentrations of 10 mg / l, 5 mg / l, 2.5 mg / l, or 1 mg / l (the latter concentration was only used for C-2). Cmp-1 was only tested at 10 mg / l. For the control experiment, no substance was added. In each case, ammonia (24.5%) was used to set the pH to 9.2 (+ / - 0.05). 200 ml of the test water was taken out for separate analysis and the remaining 1.5 liters was filled into the boiler. With all valves closed, the stirring speed was set to 150 rpm and the test water in the boiler was heated to 252 °C and held at this temperature and the resulting pressure of 40 bar (4 MPa) for 24 hours. Samples were taken from the vapor phase at the time of reaching the required temperature and subsequently after 2 hours, 20 hours, 22 hours, and 24 hours. The last sample was taken from the boiler vessel after shutdown (i.e., after pressure release and cooling).

[0266] The total iron content in the samples was determined by FAAS (flame atomic absorption spectrometry). For this purpose, the samples were shaken and 10 ml was transferred to a 15 ml test tube. 0.5 ml of HCl (32%) was added and then the test tube was heated to 170 °C for 30 minutes. After cooling, the iron concentration was measured by FAAS. The detection limit of this method is 0.1 mg Fe / l. The results are compiled in Table 4.

[0267] Table 4: Total iron content in the vapor of a pilot boiler operating at 252 °C and 40 bar (4 MPa)

[0268] C-1 [10 ppm] a b c d e f g n.d. C-2 [10 ppm] <0.1 <0.1 0.3 0.23 0.18 <0.1 n.d. Cmp-1 [10 ppm] 0.1 <0.1 <0.1 <0.1 <0.1 <0.1 n.d. n.d. C-1 [5 ppm] <0.1 2.8 7.7 6.2 3.3 n.d. <0.1 <0.1 <0.1 C-2 [5 ppm] <0.1 <0.1 <0.1 n.d. <0.1 <0.1 C-1 [2.5 ppm] <0.1 <0.1 <0.1 <0.1 n.d. <0.1 <0.1 C-2 [2.5 ppm] <0.1 <0.1 <0.1 <0.1 n.d. <0.1 <0.1 <0.1 C-2 [1 ppm] <0.1 <0.1 <0.1 n.d. n.d. n.d. n.d. n.d. <0.1 DI water* 0.1 n.d. <0.1 <0.1 Example 4: Corrosion test of compositions P-1 and P-2 on the surface of carbon steel at 252 °C (40 bar; 4 MPa) 1.5 6.8 7.9 4.6

[0269] a Fe concentration in the solution before heat treatment [mg / l]

[0270] b Fe concentration in the vapor after reaching 252 °C [mg / l]

[0271] c Fe concentration in the vapor after 2 hours [mg / l]

[0272] d Fe concentration in the vapor after 20 hours [mg / l]

[0273] e Fe concentration in the vapor after 22 hours [mg / l]

[0274] f Fe concentration in the vapor after 24 hours [mg / l]

[0275] g Fe concentration in the boiler water after shutdown [mg / l]

[0276] * Deionized water; alkalized to pH 9.2

[0277] n.d. Not determined

[0278] It can be seen that the Fe concentration in the steam generated from the water treated with N-acyl sarcosine C-1 and C-2 is significantly lower than that in the untreated water and the water treated with oleylamine.

[0279] The corrosion rate of the steel specimens was determined as follows: After shutdown, the specimens were removed from the boiler and the corrosion products and deposits were roughly removed with water and a soft brush. Then the specimens were cleaned with an acid pickling solution (consisting of 230 ml of HCl (37%), 5 ml of PP (containing propoxylated propargyl alcohol; from BASF SE) and 765 ml of deionized water) for 3 minutes, carefully rinsed first with deionized water and then with ethanol, dried at 105 °C and weighed. It must be noted that the average loss of the steel specimens due to acid pickling was 0.45 mg / min of pickling time. The corrosion rate CR in mm / a was calculated using the following formula from the weight loss (d weight [mg]):

[0280] Formula 1

[0281]

[0282] For steel St 37, f is 0.028.

[0283] The results are compiled in Table 5.

[0284] Table 5: Corrosion rates of specimens placed in the vapor phase of a pilot boiler operating at 252 °C and 40 bar (4 MPa)

[0285]

[0286]

[0287] Specimen No.:

[0288] 11, 12, and 13 refer to treatment with C-1 at 10 ppm (11), 5 ppm (12), and 2.5 ppm (13). 21, 22, 23, and 24 refer to treatment with C-2 at 10 ppm (21), 5 ppm (22), 2.5 ppm (23), and 1 ppm (24). Cmp-11 refers to treatment with Cmp-1 at 10 ppm. DI refers to no treatment (however, alkalized to pH 9.2 similar to the treated water).

[0289] Details:

[0290] 11a / b, 12a / b, and 13a / b refer to specimens placed in the steam; the water treatment was carried out with C-1 at 10 ppm (11), 5 ppm (12), and 2.5 ppm (13), respectively.

[0291] 21a / b, 22a / b, 23a / b, and 24a / b refer to specimens placed in steam; water treatment is carried out with C-2 at 10 ppm (21), 5 ppm (22), 2.5 ppm (23), and 1 ppm (24) respectively.

[0292] Cmp-11a / b refers to specimens placed in steam; water treatment is carried out with Cmp-1 at 10 ppm.

[0293] DI-1a / b refers to specimens placed in steam; no water treatment.

[0294] It can be seen that the corrosion rate of specimens placed in the steam generated by water treated with N-acyl sarcosine C-1 and C-2 is significantly lower than that of untreated water and water treated with oleylamine.

[0295] Example 5: Corrosion test of composition P-2 on the surface of carbon steel at 277 °C (60 bar; 6 MPa)

[0296] Fe [mg / l]

[0297] Two specimens of low-carbon steel C1010 (steel St 37) with a length of 16.6 cm 2 are placed in the boiler vessel (aqueous phase), and another two specimens are suspended in the steam phase. The composition to be tested is added to 1.7 liters of ultrapure water (18.2 mΩ) to obtain a concentration of 500 mg / l (= 10 mg / l of active compound C-1 or C-2). 200 ml of the test water is taken out for separate analysis and the remaining 1.5 liters are loaded into the boiler. All valves are closed, the stirring speed is set to 150 rpm, and the test water in the boiler is heated to 252 °C and maintained at this temperature and the resulting pressure of 40 bar (4 MPa) for 96 hours. Samples are extracted from the aqueous and steam phases after 2 hours, 48 hours, 72 hours, and 96 hours. The last sample is extracted from the boiler vessel after shutdown (i.e., after pressure release and cooling).

[0298] The total iron content in the samples is determined by FAAS (flame atomic absorption spectrometry). For this purpose, the samples are shaken and 10 ml are transferred to a 15 ml test tube. 0.5 ml of HCl (32%) is added, and then the test tube is heated to 170 °C for 30 minutes. After cooling, the iron concentration is measured by FAAS. The detection limit of this method is 0.1 mg Fe / l. The results are compiled in Table 6.

[0299] Table 6: Total iron content in steam and water of a pilot boiler operating at 252 °C and 40 bar (4 MPa)

[0300]

[0301] Fe concentration in steam after 2 h [mg / l]

[0302] Fe concentration in water after 2 h of h2 [mg / l]

[0303] Fe concentration in steam after 48 h of j1 [mg / l]

[0304] Fe concentration in water after 48 h of j2 [mg / l]

[0305] Fe concentration in steam after 72 h of k1 [mg / l]

[0306] Fe concentration in water after 72 h of k2 [mg / l]

[0307] Fe concentration in steam after 96 h of l1 [mg / l]

[0308] Fe concentration in water after 96 h of l2 [mg / l]

[0309] Fe concentration in boiler water after shutdown [mg / l]

[0310] The corrosion rate of the steel specimen was determined as follows: After shutdown, the specimen was removed from the boiler and the corrosion products and deposits were roughly removed with water and a soft brush. Then the specimen was cleaned with an acid pickling solution (consisting of 230 ml of HCl (37 %), 5 ml PP (containing propoxylated propargyl alcohol; from BASF SE) and 765 ml of deionized water) for 3 minutes, carefully rinsed first with deionized water and then with ethanol, dried at 105 °C and weighed. It must be noted that the average loss of the steel specimen due to acid pickling was 0.45 mg / min of pickling time. From the weight loss (d weight [mg]) the corrosion rate CR in mm / a was calculated using the following formula:

[0311] Formula 2

[0312]

[0313] For steel St 37, f is 0.028.

[0314] The results are compiled in Table 7.

[0315] Table 7: Corrosion rates of specimens placed in the steam and water phases of a pilot boiler operating at 252 °C and 40 bar (4 MPa)

[0316]

[0317]

[0318] Specimen No.:

[0319] S refers to the test piece placed in steam, and W refers to the test piece placed in water. 11 refers to treatment with P-1. 21 refers to treatment with P-2.

[0320] Details:

[0321] S-P-11a and S-P-11b refer to two test pieces (a and b) placed in steam; water treatment is carried out with 500 ppm of P-1.

[0322] W-P-11a and W-P-11b refer to two test pieces (a and b) placed in water; water treatment is carried out with 500 ppm of P-1.

[0323] S-P-21a and S-P-21b refer to two test pieces (a and b) placed in steam; water treatment is carried out with 500 ppm of P-2.

[0324] W-P-21a and W-P-21b refer to two test pieces (a and b) placed in water; water treatment is carried out with 500 ppm of P-2.

[0325] DI water*

[0326] Two 16.6 cm 2 low-carbon steel C1010 test pieces (steel St 37) are suspended in the steam phase of a pilot boiler. The composition P-2 is added to 1.7 liters of ultrapure water (18.2 mΩ) to obtain a concentration of 500 mg / l (= 10 mg / l of the active compound C-2). For the comparative test, deionized water alkalized with 135 ppm of diethyl ethanolamine is used. 200 ml of the test water is taken out for separate analysis and the remaining 1.5 liters are filled into the boiler. All valves are closed, the stirring speed is set to 150 rpm and the test water in the boiler is heated to 277 °C and held at this temperature and the resulting pressure of 60 bar (6 MPa) for 72 hours. Samples are extracted from the water phase and the steam phase after 2 hours, 24 hours, 48 hours and 72 hours. The last sample is extracted from the boiler vessel after shutdown (i.e., after pressure release and cooling).

[0327] The total iron content in the samples is determined by FAAS (flame atomic absorption spectrometry). For this purpose, the samples are shaken and 10 ml are transferred to a 15 ml test tube. 0.5 ml of HCl (32%) is added, and then the test tube is heated to 170 °C for 30 minutes. After cooling, the iron concentration is measured by FAAS. The detection limit of this method is 0.1 mg Fe / l. The results are compiled in Table 8.

[0328] Table 8: Total iron content in the steam of a pilot boiler operating at 277 °C and 60 bar (6 MPa)

[0329] n.d. n o p q r P-2 0.16 <0.1 <0.1 <0.1 0.17 Specimen Weight before treatment [g] 3.7 16 9.7 0.99

[0330] n Fe concentration in steam after 2 h [mg / l]

[0331] o Fe concentration in steam after 24 h [mg / l]

[0332] p Fe concentration in steam after 48 h [mg / l]

[0333] q Fe concentration in steam after 72 h [mg / l]

[0334] r Fe concentration in boiler water after shutdown [mg / l]

[0335] * Deionized water; alkalized with 135 ppm diethylethanolamine

[0336] The corrosion rate of the steel specimens was determined as follows: After shutdown, the specimens were removed from the boiler and roughly cleaned of corrosion products and deposits with water and a soft brush. The specimens were then cleaned for 3 minutes with an acid pickling solution (consisting of 230 ml HCl (37 %), 5 ml PP (containing propoxylated propargyl alcohol; from BASF SE) and 765 ml deionized water), carefully rinsed first with deionized water and subsequently with ethanol, dried at 105 °C and weighed. It should be noted that the average loss of the steel specimens due to pickling was 0.45 mg / min pickling time.

[0337] The corrosion rate CR in mm / a was calculated from the weight loss (d weight [mg]) using the following formula:

[0338] Formula 3

[0339]

[0340] For steel St 37, f is 0.028.

[0341] The results are compiled in Table 9.

[0342] Table 9: Corrosion rates of specimens placed in the steam phase of a pilot boiler operating at 277 °C and 60 bar (6 MPa)

[0343] Weight after pickling [g] Corrosion rate [mm / a] P-21c P-21d DI-1c 8.6067 8.6061 0.0056 DI-1d 8.5912 8.5902 0.0093 Example 6: Corrosion test of compositions P-1, P-2, and Cmp-P-1 on the surface of copper at 252 °C (40 bar; 4 MPa) 8.6761 8.6548 0.1988 Cu [mg / l] 8.7009 8.6791 0.2035

[0344] Specimen number:

[0345] 21 refers to treatment with P-2. DI refers to no treatment (but alkalized with 135 ppm diethylethanolamine).

[0346] Details:

[0347] P-21c and P-21d refer to two test specimens (c and d) placed in steam; the water treatment is carried out with P-2 at 500 ppm.

[0348] DI-1c and DI-1d refer to two test specimens (c and d) placed in steam; there is no water treatment.

[0349] P-1 [125 ppm] P-2 [125 ppm]

[0350] Two copper test specimens (copper SF-Cu; CDA 110; 99.9 wt% Cu, 0.04 wt% O) are suspended in the steam phase of a pilot boiler. The composition to be tested is added to 1.7 liters of ultrapure water (18.2 mΩ) to obtain a concentration of 500 mg / l (=10 mg / l of Cmp-1) or 125 mg / l (=2.5 mg / l of active compound C-1 or C-2). For the comparative test, deionized water alkalized with 135 ppm of diethyl ethanolamine is used. 200 ml of the test water is taken out for separate analysis and the remaining 1.5 liters are loaded into the boiler. All valves are closed, the stirring speed is set to 150 rpm and the test water in the boiler is heated to 252 °C and held at this temperature and the resulting pressure of 40 bar (4 MPa) for 72 hours. Samples are extracted from the steam phase after 2 hours, 24 hours, 48 hours and 72 hours. The last sample is extracted from the boiler vessel after shutdown (i.e., after pressure release and cooling).

[0351] The total copper content in the samples is determined by FAAS (flame atomic absorption spectrometry). For this purpose, the samples are shaken and 10 ml are transferred to a 15 ml test tube. 0.5 ml of HCl (32%) is added and then the test tube is heated to 170 °C for 30 minutes. After cooling, the Cu concentration is measured by FAAS. The detection limit of this method is 0.1 mg Cu / l. The results are compiled in Table 10.

[0352] Table 10: Total copper content in the steam of a pilot boiler operating at 252 °C and 40 bar (4 MPa)

[0353] Cmp-P-1 [500 ppm] s t u v w DI water* <0.1 <0.1 <0.1 <0.1 <0.1 n.d. <0.1 <0.1 <0.1 <0.1 0.10 Specimen <0.1 0.54 0.25 0.13 0.27 Weight before treatment [g] Weight after pickling [g] 0.5 0.51 0.46 0.54

[0354] s Cu concentration in steam after 2 hours [mg / l]

[0355] t Cu concentration in steam after 24 hours [mg / l]

[0356] u Cu concentration in steam after 48 hours [mg / l]

[0357] v Cu concentration in steam after 72 hours [mg / l]

[0358] Cu concentration in boiler water after shutdown [mg / l]

[0359] * Deionized water; alkalinized with 135 ppm diethylethanolamine

[0360] The corrosion rate of the copper specimens was determined as follows: After shutdown, the specimens were removed from the boiler and the corrosion products and deposits were roughly removed with water and a soft brush. Then the specimens were cleaned for 3 minutes with an acid cleaning solution (consisting of 100 grams of 8621 (containing amidosulfuric acid); and 900 grams of deionized water), carefully rinsed first with deionized water and then with ethanol, dried at 105 °C and weighed. It should be noted that the average loss of the copper specimens due to acid cleaning was 0.12 mg / minute of acid cleaning time.

[0361] From the weight loss (d weight [mg]), the corrosion rate CR in mm / a was calculated using the following formula:

[0362] Formula 4

[0363]

[0364] The f of copper SF-Cu is 0.024.

[0365] The results are compiled in Table 11.

[0366] Table 11: Corrosion rates of specimens placed in the vapor phase of a pilot boiler operating at 252 °C and 40 bar (4 MPa)

[0367] Corrosion rate [mm / a] P-11e P-11f P-22e P-22f 9.5444 9.5430 0.0112 Cmp-P-11e 9.5687 9.5674 0.0104 Cmp-P-11f 9.5722 9.5710 0.0096 DI-1e 9.5554 9.5542 0.0096 DI-1f 9.5244 9.5215 0.0232 Example 7: Corrosion test of non-formulated products C-2 and Cmp-2 on the surface of carbon steel at 311 °C (100 bar; 10 MPa) 9.4922 9.4896 0.0208 Fe [mg / l] 9.5132 9.5097 0.0280 C-2 [2.5 ppm] 9.5601 9.5573 0.0224

[0368] Specimen number:

[0369] 11 refers to treatment with 125 ppm of P-1. 22 refers to treatment with 125 ppm of P-2. Cmp-P-11 refers to treatment with 500 ppm of Cmp-P-1. DI refers to no treatment (but alkalinized with 135 ppm of diethylethanolamine).

[0370] Details:

[0371] P-11e and P-11f refer to two specimens (e and f) placed in the vapor; water treatment with 125 ppm of P-1.

[0372] P-22e and P-22f refer to two specimens (e and f) placed in the vapor; water treatment with 125 ppm of P-2.

[0373] Cmp-P-11e and Cmp-P-11f refer to two test specimens (e and f) placed in steam; water treatment was carried out with 500 ppm of Cmp-P-1.

[0374] DI-1e and DI-1f refer to two test specimens (e and f) placed in steam; there was no water treatment.

[0375] Cmp-2 [2.5 ppm] DI water*

[0376] Two 16.6 cm 2 low-carbon steel C1010 test specimens (steel St 37) were suspended in the steam phase of a pilot boiler. The substance to be tested was added to 1.7 liters of ultrapure water (18.2 mΩ) to obtain a concentration of 2.5 mg / l. In each case, the pH was set to 9.2 (+ / - 0.05) with ammonia (24.5%). 200 ml of the test water was taken out for separate analysis and the remaining 1.5 liters was filled into the boiler. With all valves closed, the stirring speed was set to 150 rpm and the test water in the boiler was heated to 311 °C and held at this temperature and the resulting pressure of 100 bar (10 MPa) for 24 hours. Samples were taken from the steam phase and the boiler water phase at the time of reaching the required temperature and subsequently after 2 hours, 4 hours, and 24 hours. The last sample was taken from the boiler vessel after shutdown (i.e., after pressure release and cooling).

[0377] The total iron content in the samples was determined by FAAS (flame atomic absorption spectrometry). For this purpose, the samples were shaken and 10 ml was transferred to a 15 ml test tube. 0.5 ml of HCl (32%) was added, and then the test tube was heated to 170 °C for 30 minutes. After cooling, the iron concentration was measured by FAAS. The detection limit of this method is 0.1 mg Fe / l. The results are compiled in Table 12.

[0378] Table 12: Total iron content in the steam of a pilot boiler operating at 311 °C and 100 bar (10 MPa)

[0379] aa bb cc dd ee <0.1 <0.1 <0.1 ff <0.1 0.12 <0.1 gg <0.1 <0.1 <0.1 hh <0.1 0.25 0.96 ii <0.1 <0.1 <0.1 jj <0.1 0.37 1.9 Example 8: Corrosion test of C-2 and Cmp-2 in a power plant <0.1 <0.1 <0.1 Example 9: Determination of the concentration of C-2 in a water sample without chloride interference 0.24 1.00 14.9 Figure 2 <0.1 <0.1 <0.1 Example 10: Determination of the concentration of C-2 in a water sample with chloride interference <0.1 0.15 6.4

[0380] aa Fe concentration in the solution before heat treatment [mg / l]

[0381] bb Fe concentration in the steam after reaching 311 °C [mg / l]

[0382] cc Fe concentration in the boiler water after reaching 311 °C [mg / l]

[0383] dd Fe concentration in the steam after 2 hours [mg / l]

[0384] ee Fe concentration in the boiler water after 2 hours [mg / l]

[0385] Fe concentration in steam after 4 h [mg / l]

[0386] Fe concentration in boiler water after 4 h [mg / l]

[0387] Fe concentration in steam after 24 h [mg / l]

[0388] Fe concentration in boiler water after 24 h [mg / l]

[0389] Fe concentration in boiler water after shutdown [mg / l]

[0390] * Deionized water; alkalized to pH 9.2

[0391] It can be seen that the Fe concentration in the steam generated from the water treated with N-acylsarcosine C-2 is significantly lower than that in the steam generated from the untreated water and also lower than that in the steam generated from the water treated with oil-based propylenediamine.

[0392] The corrosion rate of the steel specimens was determined as follows: After shutdown, the specimens were removed from the boiler and the corrosion products and deposits were roughly removed with water and a soft brush. Then the specimens were cleaned with an acid wash solution (consisting of 230 ml of HCl (37%), 5 ml PP (containing propoxylated propargyl alcohol; from BASF SE) and 765 ml of deionized water) for 3 minutes, carefully rinsed first with deionized water and then with ethanol, dried at 105 °C and weighed. It should be noted that the average loss of the steel specimens due to acid washing was 0.45 mg / min of acid washing time. The corrosion rate CR in mm / a was calculated from the weight loss (d weight [mg]) using the following formula:

[0393] Formula 5

[0394]

[0395] For steel St 37, f is 0.028.

[0396] The results are compiled in Table 13.

[0397] Table 13: Corrosion rates of specimens in the vapor phase and water phase of a pilot boiler operating at 311 °C and 100 bar (10 MPa)

[0398]

[0399]

[0400] Specimen No.:

[0401] S refers to the test piece placed in steam, and W refers to the test piece placed in water. 25 refers to treatment with C-2 at 2.5 ppm. Cmp-25 refers to treatment with Cmp-2 at 2.5 ppm. DI refers to no treatment (however, similar to treated water, alkalized to pH 9.2).

[0402] Details:

[0403] S-25a and S-25b refer to two test pieces (a and b) placed in steam; water treatment is carried out with C-2 at 2.5 ppm respectively.

[0404] W-25a and W-25b refer to two test pieces (a and b) placed in water; water treatment is carried out with C-2 at 2.5 ppm respectively.

[0405] Cmp-S-25a and Cmp-S-25b refer to two test pieces (a and b) placed in steam; water treatment is carried out with Cmp-2 at 2.5 ppm respectively.

[0406] Cmp-W-25a and Cmp-W-25b refer to two test pieces (a and b) placed in water; water treatment is carried out with Cmp-2 at 2.5 ppm respectively.

[0407] S-DI-a and S-DI-b refer to two test pieces (a and b) placed in steam; there is no water treatment.

[0408] W-DI-a and W-DI-b refer to two test pieces (a and b) placed in water; there is no water treatment.

[0409] It can be seen that the corrosion rate of the test pieces placed in the water treated with N-acyl sarcosine C-2 and the steam generated by this water is significantly lower than that of the untreated water and the water treated with oil-based propylenediamine.

[0410] Figure 2

[0411] The test was carried out in a shell boiler with a design pressure of 15 bar (1.5 MPa) and usually operating at 10 bar (1 MPa) under low load conditions. At the start of the test, the boiler had been in normal, established operation for several years, using water with oil-based propylenediamine (Cmp-2) continuously metered in. Oil-based propylenediamine is a standard corrosion inhibitor that provides good corrosion protection. Between January 10, 2020 and July 28, 2020, the Fe concentration in the steam condensate was measured weekly as a measure of corrosion. During this period, the pump was operated at 60% of the pump stroke (dose rate 1.5 l / h).

[0412] On July 28, 2020, the treatment with C-2 was started by ceasing the addition of Cmp-2 and instead continuously adding C-2 to the feed water in the same amount as the previously added Cmp-2. By September 16, 2020, Cmp-2 had been completely replaced by C-2. The period between July 28, 2020 and September 16, 2020 is hereinafter referred to as the "transition period". During this transition period, the Fe concentration in the steam condensate was further monitored weekly. During this period, the pump was operated at 30% pump stroke (dose rate 0.8 l / h).

[0413] September 16, 2020 was considered the starting point of the C-2 treatment. The current results were obtained until April 14, 2021. On April 14, 2021, the amount of C-2 in the feed water (= returned condensate + fresh water to compensate for water losses) and in the steam condensate was determined using the method described in Example 10 below. The concentration of C-2 in the feed water was 0.16 mg / l (0.16 ppm) (the average of two determinations showed 0.15 and 0.17 mg / l), and the concentration of C-2 in the steam condensate was <0.1 mg / l (<0.1 ppm; below the detection limit) (two determinations).

[0414] The Fe concentration in the steam condensate was determined weekly as a measure of corrosion. For most of the observed C-2 treatment (until February 13, 2021), the pump was operated at 30% pump stroke; then it was increased to 60%.

[0415] To determine the Fe concentration, the operator took samples once a week. For this purpose, the sample valve was opened and the initial liquid was flashed for 1 minute to obtain a representative sample. The sample bottle was washed twice with the sample water so that the bottle surface was saturated with the corrosion inhibitor and thus the absorption of the corrosion inhibitor in the sample to be examined into the bottle surface was minimized. Using Iron Reagent Powder Pillows from Hach Lange GmbH, Germany to determine the Fe concentration.

[0416] The following table compiles the weekly average values of the Fe concentration in the steam condensate under Cmp-2 treatment, during the transition period, and under C-2 treatment.

[0417] Table 14

[0418]

[0419] The higher Fe concentration during the transition period may be attributed to the chemical desorption and adsorption processes on the surface of the device, during which Cmp-2 was gradually replaced by C-2.

[0420] Surprisingly, C-2 exhibited better anti-corrosion effect than Cmp-2, despite the fact that for most of the time of the observed C-2 treatment, the pump was operating at only 30% of the pump stroke, i.e., half of the 60% pump stroke applied during the observed Cmp-2 treatment. The reduced pump stroke means a lower rate of the corrosion inhibitor moving through the system, and thus a lower likelihood of exerting its anti-corrosion effect. Therefore, at 60% pump stroke, it can be expected that the anti-corrosion effect of C-2 would be even better.

[0421] Furthermore, it can be seen that the standard deviation of the Fe concentration was significantly lower in the case of the C-2 treatment than in the Cmp-2 treatment, meaning that C-2 provides more reliable anti-corrosion protection than Cmp-2.

[0422] Figure 2

[0423] 9.1 Preparation of the calibration curve

[0424] Prepare five test samples, each having a sample volume of 10.0 ml, containing (1.) 0.1 mg / l, (2.) 0.2 mg / l, (3.) 0.5 mg / l, (4.) 1 mg / l, and (5.) 2 mg / l of C-2 (used as a composition containing 2 wt% of C-2, 20 wt% of DEAE, and 78 wt% of water) in deionized water. Provide a blank sample containing only deionized water with a sample volume of 10.0 ml. Each test sample and the blank sample were processed as described below:

[0425] Load the sample into a 25-ml 1-inch cuvette. Add 2 ml of buffer solution pH 7.00 ± 0.02 (20 °C) (composed of potassium dihydrogen phosphate, disodium hydrogen phosphate, and water; from VWR Chemicals), then add 0.2 ml of methylene blue solution (0.05% aqueous solution) and carefully mix the solution. Fill the cuvette with 1-nonanol to the 20-ml mark (corresponding to 7.8 ml of 1-nonanol), and shake the cuvette vigorously for 10 seconds. After 7 - 9 minutes, the organic phase has separated from the aqueous phase. Carefully remove approximately 5 ml of the organic phase with a Pasteur pipette and transfer it to a 1-inch cuvette. First, the cuvette containing the organic extract from the blank sample was photometrically measured at 660 nm in a DR3900 photometer from Hach Lange GmbH, Germany for calibration; accordingly, the value obtained was set to '0' to be subtracted from the results of the test samples. Then, the cuvettes containing the organic extracts from the test samples were photometrically measured with blank calibration at 660 nm.

[0426] Plot the absorbances obtained with these five concentrations in a graph, where the concentration [mg / l] is on the x-axis (horizontal axis) and the absorbance is on the y-axis (vertical axis), and plot the regression line. The regression line is atFigure 2 Depicted as line segment A in

[0427] The slope of this line segment was determined to be 0.40540 and the extrapolated absorption at 0 mg / l was determined to be 0.0615. This gives equation (6):

[0428] Absorption = 0.40540 × Concentration C-2 + 0.0615 (6)

[0429] Thus, the unknown concentration of C-2 can be determined by solving equation (6) for the concentration:

[0430] Concentration C-2 = (Absorption - 0.0615) / 0.40540 (7)

[0431] 9.2 Determination of the unknown concentration of C-2

[0432] A 10.0 mL water test sample containing C-2 was placed into a 25 mL 1-inch cuvette. 10.0 mL of deionized water for the blank test was placed into another 25 mL 1-inch cuvette. The following steps were carried out with the test sample and the blank sample. 2 mL of buffer solution pH 7.00 ± 0.02 (20 °C) (consisting of potassium dihydrogen phosphate, disodium hydrogen phosphate, and water; from VWR Chemicals) was added, then 0.2 mL of methylene blue solution (0.05% aqueous solution) was added and the solution was carefully mixed. 1-nonanol was added to the cuvette to the 20 mL mark (corresponding to 7.8 mL of 1-nonanol), and the cuvette was shaken vigorously for 10 seconds. After 7 - 9 minutes, the organic phase had separated from the aqueous phase. Approximately 5 mL of the organic phase was carefully removed with a Pasteur pipette and transferred to a 1-inch cuvette. First, the cuvette containing the organic extract from the blank sample was photometrically measured at 660 nm in a DR3900 photometer from Hach Lange GmbH, Germany for calibration; correspondingly, the value obtained was set to '0' to subtract from the results of the test sample. Then, the cuvette containing the organic extract from the test sample was photometrically measured at 660 nm with blank calibration.

[0433] The concentration of C-2 was determined by inserting the observed absorption value into equation (7):

[0434] Concentration C-2 = (Absorption - 0.0615) / 0.40540 (7)

[0435] Figure 2

[0436] 10.1 Preparation of the calibration curve

[0437] Twenty-four test samples were prepared, each having a sample volume of 10.0 ml, containing the amounts of chloride ions (added as HCl) and C-2 (used as a composition containing 2 wt% of C-2, 20 wt% of DEAE, and 78 wt% of water) listed in the following table in deionized water, and were loaded into 25-ml 1-inch cuvettes. 10.0 ml of deionized water for the blank value test was loaded into another 25-ml 1-inch cuvette.

[0438] Table 15

[0439]

[0440]

[0441] Each test sample and the blank sample were processed as follows:

[0442] The sample was loaded into a 25-ml 1-inch cuvette. 2 ml of a buffer solution pH 7.00 ± 0.02 (20 °C) (composed of potassium dihydrogen phosphate, disodium hydrogen phosphate, and water; from VWR Chemicals) was added, then 0.2 ml of a methylene blue solution (0.05% aqueous solution) was added and the solution was carefully mixed. 1-Nonanol was loaded into the cuvette to the 20-ml mark (corresponding to 7.8 ml of 1-nonanol), and the cuvette was shaken vigorously for 10 seconds. After 7 - 9 minutes, the organic phase had separated from the aqueous phase. Approximately 5 ml of the organic phase was carefully removed with a Pasteur pipette and transferred to a 1-inch cuvette. First, the cuvette containing the organic extract from the blank sample was photometrically measured at 660 nm in a DR3900 photometer from Hach Lange GmbH, Germany for calibration; correspondingly, the value obtained was set to '0' to be subtracted from the results of the test samples. Then, the cuvette containing the organic extract from the test samples was photometrically measured at 660 nm with blank calibration.

[0443] The absorption obtained with these five or six Cl - concentrations was plotted in a graph, where the concentration of C-2 [mg / l] was on the x-axis (horizontal axis) and the absorption was on the y-axis (vertical axis); a regression line was plotted.

[0444] conc. Cl - The regression line for conc. Figure 2 = 31 mg / l is depicted as line segment B.

[0445] conc. Cl - The regression line for conc. Figure 2 = 62 mg / l is depicted as line segment C.

[0446] conc.Cl - The regression line for = 156 mg / l is depicted as line segment D in Figure 3 .

[0447] conc. Cl - The regression line for = 218 mg / l is depicted as line segment E in Example 11: Determination of the concentration of C-2 in a water sample with chloride and bicarbonate interference .

[0448] conc. Cl - The regression line for = 311 mg / l is depicted as line segment F in ​ .

[0449] Plot the absorbance values of line segments A to F in ​ at conc. C-2 = 0 mg / l in a graph, where the concentration of Cl - [mg / l] is on the x-axis (horizontal axis) and the absorbance is on the y-axis (vertical axis); plot the regression line; see ​ .

[0450] Determine the slope of this line segment to be 0.00107 and the extrapolated absorbance at 0 mg / l to be 0.0727. This gives equation (8):

[0451] Absorbance = 0.00107 × Concentration Cl - + 0.0727 (8)

[0452] Combining equations (7) and (8) gives equation (9) (Note: As the ordinate intercept = the extrapolated absorbance at 0 mg / l, use the value from equation (8) (0.0727) because it was determined using more data points compared to the value used in equation (7) and is thus considered more accurate):

[0453] Absorbance = 0.40540 × Concentration C-2 + 0.00107 × Concentration Cl - + 0.072 (9)

[0454] Solving equation (9) for the C-2 concentration gives the following equation (10):

[0455] Formula 6

[0456]

[0457] 10.2 Determination of the unknown concentration of C-2 in water containing chloride ions

[0458] The chloride ion concentration in the water to be tested is determined using a commercial test strip from Hach Lange GmbH, Germany. 10.0 mL of the water test sample containing C-2 and chloride ions is placed into a 25 mL 1-inch cuvette. 10.0 mL of deionized water for the blank value test is placed into another 25 mL 1-inch cuvette. The following steps are carried out with the test sample and the blank sample. Add 2 mL of a buffer solution pH 7.00 ± 0.02 (20 °C) (consisting of potassium dihydrogen phosphate, disodium hydrogen phosphate, and water; from VWR Chemicals), then add 0.2 mL of methylene blue solution (0.05% aqueous solution) and carefully mix the solution. Fill the cuvette with 1-nonanol up to the 20 mL mark (corresponding to 7.8 mL of 1-nonanol), and shake the cuvette vigorously for 10 seconds. After 7 - 9 minutes, the organic phase has separated from the aqueous phase. Carefully remove approximately 5 mL of the organic phase with a Pasteur pipette and transfer it to a 1-inch cuvette. First, the cuvette containing the organic extract from the blank sample is photometrically measured at 660 nm in a DR3900 photometer from Hach Lange GmbH, Germany for calibration; accordingly, the value obtained is set to '0' to be subtracted from the results of the test sample. Then, the cuvette containing the organic extract from the test sample containing C-2 is photometrically measured with blank calibration at 660 nm.

[0459] The concentration of C-2 is determined by inserting the observed absorption value into the following equation (11):

[0460] Formula 7

[0461]

[0462] conc. = concentration

[0463] ​

[0464] A calibration curve is prepared similar to Example 10.1. The linear combination gives the following equation (12):

[0465] Formula 8

[0466] (12)

[0468] c = concentration

Claims

1. A method for providing corrosion protection to a pressurized water-steam system, the method comprising adding an N-acylsarcosine compound of formula (I) or a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof R-C(=O)-N(CH3)-CH2-COOH(I) wherein R is a straight-chain or branched acyclic hydrocarbon group having from 10 to 24 carbon atoms; wherein in the case of using a mixture of different N-acylsarcosine compounds of formula (I), in up to 30% by weight of the N-acylsarcosine compound (I) based on the total weight of the mixture, R is a straight-chain or branched acyclic hydrocarbon group having from 4 to 9 carbon atoms; wherein the N-acylsarcosine compound of formula (I), the mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water used to operate the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 10 mg / kg, wherein the pressure in the water-steam system during operation is at least 1 MPa.

2. A method for providing corrosion protection to a pressurized water-steam system, the method comprising adding an N-acylsarcosine compound of formula (I) or a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof R-C(=O)-N(CH3)-CH2-COOH(I) wherein R is a straight-chain or branched acyclic hydrocarbon group having from 10 to 24 carbon atoms; wherein in the case of using a mixture of different N-acylsarcosine compounds of formula (I), in up to 30% by weight of the N-acylsarcosine compound (I) based on the total weight of the mixture, R is a straight-chain or branched acyclic hydrocarbon group having from 4 to 9 carbon atoms; wherein the N-acylsarcosine compound of formula (I), the mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water used to operate the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 10 mg / kg, wherein the water-steam system is a geothermal system and the pressure of the water-steam system is from 0.2 to 6 MPa.

3. The method according to claim 1 or 2, wherein the N-acylsarcosine compound of formula (I), the mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water used to operate the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 8 mg / kg.

4. The method according to claim 3, wherein the N-acylsarcosine compound of formula (I), the mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water used to operate the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.02 to 6 mg / kg.

5. The method according to claim 3, wherein the N-acylsarcosine compound of formula (I), a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water for operating the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.05 to 5 mg / kg.

6. The method according to claim 3, wherein the N-acylsarcosine compound of formula (I), a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water for operating the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.1 to 5 mg / kg.

7. The method according to claim 3, wherein the N-acylsarcosine compound of formula (I), a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water for operating the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.5 to 5 mg / kg.

8. The method according to claim 3, wherein the N-acylsarcosine compound of formula (I), a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water for operating the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.5 to 3.5 mg / kg.

9. The method according to claim 5, wherein the N-acylsarcosine compound of formula (I), a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water for operating the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.5 to 3 mg / kg.

10. The method according to claim 5, wherein the N-acylsarcosine compound of formula (I), a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the water for operating the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.8 to 2.5 mg / kg.

11. The method according to claim 1 or 2, which is used to provide corrosion protection to those components of the pressurized water-steam system that are in contact with steam and / or with condensate.

12. The method according to claim 1 or 2, which is used to provide corrosion protection to those components of the pressurized water-steam system that are in contact with steam and also with condensate.

13. The method according to claim 1 or 2, wherein the pressurized water-steam system has an inner surface made of or containing the following materials: ferrous materials; copper, copper alloys, aluminum, aluminum alloys or two or more of these materials.

14. The method according to claim 13, wherein the ferrous material is steel.

15. The method according to claim 13, wherein the pressurized water-steam system has an inner surface made of or containing the following materials: steel, copper or steel and copper.

16. A method according to claim 1 or 2, wherein R in formula (I) is selected from C 12 -C 20 -alkyl and C 12 -C 20 -alkenyl having 1, 2 or 3 C═C double bonds, where in the case of using a mixture of N-acylsarcosine compounds of different formula (I), in up to 25% by weight of the N-acylsarcosine compound (I) based on the total weight of the mixture, R is C5-C9 alkyl; and in up to 55% by weight of the N-acylsarcosine compound (I) based on the total weight of the mixture, R is selected from C 10 -C 11 -alkyl and C 10 -C 11 -alkenyl.

17. The method according to claim 1 or 2, wherein R in formula (I) on average has from 12 to 18 carbon atoms.

18. The method according to claim 1 or 2, which comprises adding an N-acylsarcosine compound of formula (I) or a salt thereof in which R is derived from oleic acid, or which comprises adding a mixture of different N-acylsarcosine compounds of formula (I) or salts thereof, wherein said mixture is derived from coconut oil.

19. The method according to claim 1 or 2, wherein the compound of formula (I) is added in its acid form to the water for operating a water-steam system.

20. The method according to claim 1 or 2, wherein the compound of formula (I) is added in salt form to the water for operating a water-steam system.

21. The method according to claim 20, wherein the compound of formula (I) is added in the form of an ammonium salt or a substituted ammonium salt to the water for operating a water-steam system.

22. The method according to claim 1 or 2, wherein the compound of formula (I) is added in the form of an aqueous solution or emulsion of the acid form of the compound of formula (I) or its ammonium salt or substituted ammonium salt to the water for operating a water-steam system.

23. The method according to claim 22, wherein the concentration of the compound of formula (I) in the aqueous solution or emulsion is in the range from 0.5 to 10% by weight, calculated as the acid form of the compound of formula (I) and based on the total weight of the aqueous solution or emulsion.

24. The method according to claim 22, wherein the aqueous solution or emulsion consists to at least 99.9% of a mixture of the compound of formula (I), water and optionally ammonia and / or at least one organic amine.

25. The method according to claim 23, wherein the aqueous solution or emulsion consists to at least 99.9% of a mixture of the compound of formula (I), water and optionally ammonia and / or at least one organic amine.

26. The method according to claim 1 or 2, wherein the pressure in the water-steam system during operation is at least 2 MPa.

27. The method according to claim 26, wherein the pressure in the water-steam system during operation is at least 3 MPa.

28. The method according to claim 1, wherein the water-steam system is a water-steam circuit.

29. The method according to claim 28, wherein the water-steam system comprises a boiler.

30. The method according to claim 29, wherein the water-steam system comprises a drum boiler or a once-through steam generator.

31. The method according to claim 29, wherein the water-steam system is a water-steam circuit, wherein during operation of the water-steam circuit, the pH value of the water in the range from 7.5 to 12 measured at 20 °C is maintained.

32. The method according to claim 29, wherein the water-steam system is a water-steam circuit, wherein during operation of the water-steam circuit, the pH value of the water in the range from 8.0 to 11 measured at 20 °C is maintained.

33. The method according to claim 29, wherein the water-steam system is a water-steam circuit, and during the operation of the water-steam circuit, the pH value of the water, measured at 20 °C, is maintained within the range of pH 8.5 to 10.

34. The method according to claim 29 or 31, wherein the water-steam system is a water-steam circuit, and during the operation of the water-steam circuit, the water contained in the water-steam circuit has a conductivity of at most 30 μS / cm, measured at 22 °C.

35. The method according to claim 1, which is used to provide corrosion protection for a pressurized water-steam system for generating steam, and the steam is used for the direct or indirect processing of food, cosmetics or pharmaceuticals.

36. The method according to claim 2, wherein an N-acylsarcosine compound or a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof is added to the production well of a geothermal power plant.

37. Use of an N-acylsarcosine compound or a mixture of N-acylsarcosine compounds of formula (I) or a salt thereof, as defined in the method according to any one of claims 1 and 16-21, for providing corrosion protection for a pressurized water-steam system, wherein the pressure in the water-steam system during operation is at least 1 MPa; wherein the use comprises adding an N-acylsarcosine compound or a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof to the water used to operate the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is within the range of 0.01 to 10 mg / kg.

38. The use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is within the range of 0.01 to 8 mg / kg.

39. The use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is within the range of 0.02 to 6 mg / kg.

40. The use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is within the range of 0.02 to 5 mg / kg.

41. The use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is within the range of 0.05 to 5 mg / kg.

42. The use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is within the range of 0.1 to 5 mg / kg.

43. The use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is within the range of 0.5 to 5 mg / kg.

44. The use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is within the range of 0.5 to 3.5 mg / kg.

45. Use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.5 to 3 mg / kg.

46. Use according to claim 37, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.8 to 2.5 mg / kg.

47. Use of an N-acylsarcosine compound or a mixture of N-acylsarcosine compounds of formula (I) or a salt thereof, as defined in the method of any one of claims 1 and 16 - 21, for providing corrosion protection to a pressurized water-steam system, wherein the water-steam system is a geothermal system and the pressure in the water-steam system during operation is from 0.2 to 6 MPa; wherein said use comprises adding an N-acylsarcosine compound or a mixture of different N-acylsarcosine compounds of formula (I) or a salt thereof to the water used to operate the water-steam system in an amount such that the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 10 mg / kg.

48. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.01 to 8 mg / kg.

49. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.02 to 6 mg / kg.

50. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.02 to 5 mg / kg.

51. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.05 to 5 mg / kg.

52. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.1 to 5 mg / kg.

53. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.5 to 5 mg / kg.

54. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.5 to 3.5 mg / kg.

55. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.5 to 3 mg / kg.

56. Use according to claim 47, wherein the average total concentration of the compound of formula (I) in the water contained in the water-steam system is in the range of 0.8 to 2.5 mg / kg.

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