RU2486139C2 - Method of preventing scaling and corrosion in water supply systems - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods of preventing scaling and corrosion and can be used in recycling water systems. The method of preventing scaling and corrosion in water supply systems is realised by adding to the treated water a mixture of 2-phosphonobutane-1,2,4-tricarboxylic acid and mineral salt deposit inhibitor in weight ratio of 1:9-1:1, respectively. The mineral salt deposit inhibitor used is a mixture having the following composition: a sodium salt of nitrile trimethylene phosphonic acid and a sodium salt of methyliminobismethylene phosphonic acid.

EFFECT: high efficiency of inhibiting corrosion and scaling in water supply systems in the presence of oxidisable biocides.

2 cl, 6 tbl, 6 ex

Description

The invention relates to methods for preventing deposits and corrosion and can be used in systems of reverse water supply, heating, hot water supply.

A known method of inhibiting salt deposits in industrial systems of water supply, heating using the IOMS reagent [Comparative evaluation of the effectiveness of domestic and imported scale inhibitors / B.N.Driker, A.L. Vankov // "Energy saving and water treatment", No. 1, 2000, 55 -59].

However, this method is ineffective for inhibiting corrosion of structural steels, as well as when used simultaneously with oxidizing biocides, such as sodium hypochlorite, in the presence of which there is a partial destruction of the organophosphonates that make up the IOMS, and, as a result, loss of effectiveness.

Closest to the proposed technical solution is a method of inhibiting salt deposition using 2-phosphonobutane-1,2,4-tricarboxylic acid [Chemistry of organophosphonate scale growth inhibitors: 3. Physicochemical aspects of 2-phosphonobutane-1,2,4-tricarboxylate ( PBTC) and its effect on CaCO ₃ crystal growth / Konstantinos D. Demadis, Panos Lykoudis // Bioinorganic chemistry and applications. 2005. No. 3-4. S.15-17].

2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) is resistant to biocides, but not effective enough when used as a scale inhibitor and a corrosion inhibitor of structural steels.

The objective of the invention is the development of a multi-purpose inhibitor resistant to biocides.

The problem is achieved by the fact that the proposed method of preventing scaling and corrosion in water supply systems by introducing into the treated water a mixture of 2-phosphonobutane-1,2,4-tricarboxylic acid and an inhibitor of deposits of mineral salts with a mass ratio of 1: 9-1: 1, respectively.

The IOMS reagent is a mixture of complexones containing aminoalkylphosphonic groups of the following composition: sodium salt of nitrile trimethylene phosphonic acid and sodium salt of methyl iminobismethylene phosphonic acid, manufactured in the industry by the Niton chemical plant according to TU 2415-013-59945303-2009. In addition, hydroxyethylidene diphosphonic acid (OEDPK) can be used as inhibitors of mineral salt deposits - it is widely used in the power industry, PAF-13 (salts of polyphminomethylene phosphonic acid) used in the oil industry.

2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) has the structural formula:

The claimed invention is illustrated by the following examples, carried out with the aim of studying the inhibitory properties to prevent scaling and corrosion.

Example 1

Into the “softened” water of continuous casting machines (CCM) of Seversky Pipe Plant OJSC of the composition: total hardness 0.1 mEq / l, alkalinity 1.9 mEq / l, total iron 0.81 mg / l, sulfates 82 mg / l, chlorides 14.2 mg / l, suspended solids 4 mg / l, sodium hypochlorite (biocide) 10 mg / l, pH = 7.4, a composition of IOMS and PBTC was administered in a mass ratio of 1: 0 to 0: 1 in an amount of 10 mg / l The corrosion rate was measured at at a temperature of 20 ° C with stirring (1.2 m / s) in a non-flowing cell with two-electrode probes made of structural steel - st. 3 - with a corrosion meter "Expert - 004". The braking coefficient was calculated by the formula

$$K=a_0/a_j,(\mathrm{one})$$

where K is the braking coefficient;

a ₀ - corrosion rate in the control experiment (without reagent);

a _j is the corrosion rate with the reagent.

The measurement error is not more than 10%.

The data are presented in table 1.

From the data presented in table. 1, it can be seen that the composition with a mass ratio of FBTK: IOMS 1: 9-1: 1 significantly reduces the rate of corrosion. Moreover, in the claimed ratios, the oxidized biocide present in the water — sodium hypochlorite — does not adversely affect the inhibitory properties of the claimed composition. The absence of FBTC in the composition (FBTC: IOMS ratio = 0: 1) negatively affects the inhibition of corrosion processes in the presence of sodium hypochlorite. A change in the ratio FBTK: IOMS to 7: 3 and to 1:12 also negatively affects the inhibitory properties of the composition (Clause 3 and Clause 8 of Table 1).

Example 2

“Technical” water (500 ml) of Chelyabinsk Zinc Plant OJSC composition: total hardness 4.1 mEq / l, calcium hardness 2.2 mEq / l, alkalinity 2.6 mEq / l, iron 0.25 mg / l, manganese 0.02 mg / l, pH = 8.2, permanganate oxidation 6 mg / l, oxidizable biocide - dibromonitrile propionamide - 10 mg / l and composition FBTK: IOMS = 1: 0-0: 1 taken in an amount of 5 mg / l, was boiled in flasks under reflux for 2 hours. Efficiency was evaluated by the number of deposits formed on the inner surface of the flasks. Deposits were dissolved in acid, neutralized with alkali. The amount of deposits was determined by the standard method using the complexometric method.

The effectiveness of the inhibition of scaling was calculated by the formula:

$$E\%=\frac{{\mathrm{but}}_{\mathrm{to}}-{\mathrm{but}}_R}{{\mathrm{but}}_{\mathrm{to}}}\times \mathrm{one\; hundred}\%,\text{(2)}$$

where a _to - the number of deposits in the control experiment, mg;

and _p is the amount of sediment with a reagent, mg.

The data are presented in table 2.

From the data presented in table 2, it can be seen that the composition in the mass ratio of PBTK: IOMS = 1: 9-1: 1 is more effective as a scale inhibitor. If in the case of inhibition of corrosion of structural steels, the high inhibitory ability can be explained by the synergistic effect of the composition, in the case of inhibition of scaling, the presence of PBTK in the composition prevents the oxidation of the components of the IOMS to orthophosphates in the presence of an oxidizing biocide dibromonitrile propionamide. Indirect evidence of this is the presence in the composition of deposits in the absence or insufficient amount of PBTK, along with calcium carbonate, calcium phosphate in an amount up to 20% of the total sediment mass. The absence of FBTK in the composition (ratio FBTK: IOMS = 0: 1) negatively affects the inhibition of scaling processes in the presence of dibromonitrile propionamide. A change in the ratio of FBTK: IOMS to 7: 3 and FBTK: IOMS to 1:12 also negatively affects the inhibitory properties of the composition (Clause 3 and Clause 8 of Table 2).

Example 3

To the “softened” water of continuous casting machines (CCM) of Seversky Pipe Plant OJSC of the composition: total hardness 0.1 mEq / l, alkalinity 1.9 mEq / l, total iron 0.81 mg / l, sulfates 82 mg / l, chlorides 14.2 mg / l, suspended solids 4 mg / l, sodium hypochlorite (biocide) 10 mg / l, pH = 7.4, a composition of HEDPA and PBTK was introduced at a weight ratio of 1: 0 to 0: 1 in an amount of 10 mg / l. The corrosion rate was measured at a temperature of 20 ° C with stirring (1.2 m / s) in a non-flowing cell with two-electrode probes made of structural steel - Art. 3 with an Expert-004 corrosion meter.

The data are presented in table.3.

From the data presented in table 3, it can be seen that the composition with a mass ratio of FBTK: OEDFK 1: 9-1: 1 significantly reduces the rate of corrosion. Moreover, the presence of an oxidizing biocide - sodium hypochlorite - does not adversely affect the inhibitory properties of the composition in the claimed proportions.

Example 4

“Technical” water (500 ml) of Chelyabinsk Zinc Plant OJSC composition: total hardness 4.1 mEq / l, calcium hardness 2.2 mEq / l, alkalinity 2.6 mEq / l, iron 0.25 mg / l, manganese 0.02 mg / l, pH = 8.2, oxidizable permanganate 6 mg / l, oxidizable biocide-dibromonitrile propionamide 10 mg / l and composition FBTK: OEDFK = 1: 0-0: 1, taken in an amount of 5 mg / l, was boiled in flasks under reflux for 2 hours. Efficiency was evaluated by the number of deposits formed on the inner surface of the flasks. Deposits were dissolved in acid, neutralized with alkali. The amount of deposits was determined by the standard method using the complexometric method.

The data are presented in table 4.

From the data presented in table 4, it can be seen that the composition in the mass ratio of FBTK: OEDPK = 1: 9-1: 1 is more effective as a scale inhibitor. If, in the case of inhibition of corrosion of structural steels, the high inhibitory ability can be explained by the synergistic effect of the composition, in the case of inhibition of scaling, the presence of PBTK in the composition prevents the oxidation of HEDPA to orthophosphates in the presence of a biocide.

Example 5

To the “softened” water of continuous casting machines (CCM) of Seversky Pipe Plant OJSC of the composition: total hardness 0.1 mEq / l, alkalinity 1.9 mEq / l, total iron 0.81 mg / l, sulfates 82 mg / l, chlorides 14.2 mg / l, suspended solids 4 mg / l, sodium hypochlorite (biocide) 10 mg / l, pH = 7.4, a composition of PAF-13 and PBTK was introduced at a weight ratio of 1: 0 to 0: 1 in an amount of 10 mg / l. The corrosion rate was measured at a temperature of 20 ° C with stirring (1.2 m / s) in a non-flowing cell with two-electrode probes made of structural steel - st.3 Expert-004 corrosion meter.

The data are presented in table.5.

From the data presented in table 5, it can be seen that the composition at a mass ratio of FBTK: PAF-13 1: 9-1: 1 significantly reduces the rate of corrosion. Moreover, the presence of an oxidizing biocide - sodium hypochlorite does not adversely affect the inhibitory properties of the composition in the claimed proportions.

Example 6

“Technical” water (500 ml) of Chelyabinsk Zinc Plant OJSC composition: total hardness 4.1 mEq / l, calcium hardness 2.2 mEq / l, alkalinity 2.6 mEq / l, iron 0.25 mg / l, manganese 0.02 mg / l, pH = 8.2, permanganate oxidation 6 mg / l, oxidizable biocide-dibromonitrile propionamide 10 mg / l - and FBTK compositions: PAF-13 = 1: 0-0 : 1, taken in an amount of 5 mg / l, was boiled in flasks under reflux for 2 hours. Efficiency was evaluated by the number of deposits formed on the inner surface of the flasks. Deposits were dissolved in acid, neutralized with alkali. The amount of deposits was determined by the standard method using the complexometric method.

The data are presented in table.6.

From the data presented in table.6, it can be seen that the composition in the mass ratio of FBTK: PAF-13 = 1: 9-1: 1 is more effective as a scale inhibitor. If, in the case of inhibition of corrosion of structural steels, the high inhibitory ability can be explained by the synergistic effect of the composition, in the case of inhibition of scaling, the presence of PBTK in the composition prevents the oxidation of the components of PAF-13 to orthophosphates in the presence of a biocide.

As can be seen from the data presented, the inventive method allows to effectively inhibit corrosion and scaling in water supply systems in the presence of oxidizing biocides.

Table 1 Corrosion Rate in the Presence of Biocide No. p / p Composition Mass ratio Corrosion rate, microns / year Braking coefficient one Control - 202 - 2 FBTC: IOMS 0: 1 170 1,2 (analog) 3 FBTC: IOMS 1-0 132 1,5 (prototype) four FBTC: IOMS 1:12 165 1,2 (the control) 5 FBTC: IOMS 1: 9 12 16.8 (according to the invention) 6 FBTC: IOMS 3: 7 23 8.8 (according to the invention) 7 FBTC: IOMS 1: 1 22 9.2 (according to the invention) 8 FBTC: IOMS 7: 3 135 1,5 (the control)

table 2 The effect of the compositions on the inhibition of scaling No. p / p Composition Mass ratio The number of deposits, mg Efficiency,
% one The control - 18.3 0,0 2 FBTC: IOMS 0: 1 5,4 70.5 (analog) 3 FBTC: IOMS 1-0 3.2 82.5 (prototype) four FBTC: IOMS 1:12 5,4 70.5 (the control) 5 FBTC: IOMS 1: 9 0.7 96.2 (according to the invention) 6 FBTC: IOMS 3: 7 0.5 97.3 (according to the invention) 7 FBTC: IOMS 1: 1 1.4 92.3 (according to the invention) 8 FBTC: IOMS 7: 3 3.4 81.4 (the control)

Table 3 Corrosion Rate in the Presence of Biocide No. p / p Composition Mass ratio Corrosion rate, microns / year Braking coefficient one Control - 202 - 2 FBTK: OEDFK 0: 1 168 1,2 (prototype) 3 FBTK: OEDFK 1-0 132 1,5 (prototype) four FBTK: OEDFK 1: 9 48 4.2 (according to the invention) 5 FBTK: OEDFK 3: 7 53 3.8 (according to the invention) 6 FBTK: OEDFK 1: 1 52 3.9 (according to the invention) 7 FBTK: OEDFK 7: 3 140 1.4 (according to the invention)

Table 4 The effect of the compositions on the inhibition of scaling No. p / p Composition Mass ratio The number of deposits, mg Efficiency% one The control - 18.3 0,0 2 FBTK: OEDFK 0: 1 16.7 8.7 (analog) 3 FBTK: OEDFK 1-0 5.0 72.7 (prototype) four FBTK: OEDFK 1: 9 2,5 86.3 (according to the invention) 5 FBTK: OEDFK 3: 7 2,3 87.4 (according to the invention) 6 FBTK: OEDFK 1: 1 3.2 82.5 (according to the invention) 7 FBTK: OEDFK 7: 3 5.2 71.6 (according to the invention)

Table 5 Corrosion Rate in the Presence of Biocide No. p / p Composition Mass ratio Corrosion rate, microns / year Braking coefficient one Control - 202 - 2 FBTK: PAF-13 0: 1 122 1,6 (prototype) 3 FBTK: PAF-13 1-0 132 1,5 (prototype) four FBTK: PAF-13 1: 9 38 5.3 (according to the invention) 5 FBTK: PAF-13 3: 7 43 4.7 (according to the invention) 6 FBTK: PAF-13 1: 1 49 4.1 (according to the invention) 7 FBTK: PAF-13 7: 3 110 1.8 (according to the invention)

Table 6 The effect of the compositions on the inhibition of scaling No. p / p Composition Mass ratio The number of deposits, mg Efficiency% one The control - 18.3 0,0 2 FBTK: PAF-13 0: 1 12.7 30.6 (analog) 3 FBTK: PAF-13 1-0 5,0 72.7 (prototype) four FBTK: PAF-13 1: 9 2,4 86.8 (according to the invention) 5 FBTK: PAF-13 3: 7 2.2 87.9 (according to the invention) 6 FBTK: PAF-13 1: 1 2.9 84.2 (according to the invention) 7 FBTK: PAF-13 7: 3 5,0 72.7 (according to the invention)

Claims (2)

1. A method for preventing scaling and corrosion in water supply systems by introducing a mixture of 2-phosphonobutane-1,2,4-tricarboxylic acid and an inhibitor of deposits of mineral salts into the treated water in a mass ratio of 1: 9-1: 1, respectively. 2. The method according to claim 1, characterized in that a mixture of the following composition is used as an inhibitor of mineral salt deposits: the sodium salt of nitrile trimethylene phosphonic acid and the sodium salt of methyl iminobismethylene phosphonic acid.