RU2486138C2 - 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 a mineral salt deposit inhibitor and a phosphoric ester of polyethylene glycol in weight ratio of 9:1-7:3, 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: simultaneously inhibiting scaling and corrosion in highly mineralised water in "dirty" recycling water supply cycles at medium pH 4-5, fluoride content greater than 50 mg/l and gas cleaning for converter production, with suspended matter content greater than 20 g/l.

2 cl, 12 tbl, 12 ex

Description

The invention relates to methods for preventing deposits and corrosion and can be used in water recycling systems.

A known method of inhibiting salt deposits in the power system and industrial water supply systems using the IOMS reagent [Comparative evaluation of the effectiveness of domestic and imported scale inhibitors / BN Driker, A. L. Vankov // “Energy conservation and water treatment”, No. 1, 2000, 55 -59]. However, this method is ineffective for inhibiting corrosion of structural steels.

Closest to the proposed technical solution is a method of inhibiting salt deposits and corrosion using low molecular weight polymers, in particular, phosphate ester of polyethylene glycol (EFP) of the General formula:

, $$H_2{O}_{3}P-O-{(C{H}_2-C{H}_2-O-)}_n-C{H}_2-C{H}_2-{(C{H}_2-C{H}_2-O-)}_{m}P{O}_3{H}_2$$

,

where n = 5-12, m = 3-16 [Low molecular weight polymers as scale inhibitors and corrosion / BN Driker, S. A. Tarasova, A. G. Tarantaev, A. N. Obozhin // “Energy saving and water treatment ”No. 6, 2010,15-77].

However, this method is not effective enough to inhibit scaling and corrosion for water with high salinity at relatively low pH and high fluoride content.

The objective of the invention is the development of a multi-purpose inhibitor (IMN) for the simultaneous inhibition of scaling and corrosion with high salinity of water of “dirty” reverse water supply cycles at a pH of 4-5, fluoride content> 50 mg / l and gas purification of converter production containing more than 10% suspended solids 20 g / l

The problem is achieved by the fact that the proposed method of preventing scaling and corrosion in water supply systems by introducing into the water to be treated a mixture of an inhibitor of deposits of mineral salts and phosphoric acid ester of polyethylene glycol in a mass ratio of 9: 1-7: 3, respectively.

The IOMS reagent is a mixture of complexones containing aminoalkylphosphonic groups of the following composition: sodium salt of nitrile trimethylene phosphonic acid, manufactured in industry by the Cheboksary Production Association Khimprom according to TU 2439-369-05763441-2003. 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.

As the phosphate ester of polyethylene glycol AFPG used

, $$H_2{O}_{3}P-O-{(C{H}_2-C{H}_2-O-)}_n-C{H}_2-C{H}_2-{(C{H}_2-C{H}_2-O-)}_{m}P{O}_3{H}_2$$

,

where n = 5-12, m = 3-16

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

Examples of corrosion inhibition, in comparison with an analog or prototype.

Example 1

Into the water of the “dirty” reverse cycle of steelmaking (1) composition (mg / l): Ca ²⁺ - 1400; sulfates - 2700; Fe ³⁺ - 10; petroleum products - 0.4; chlorides - 150; the pH of the medium is 4.5, a composition of IOMS and EPPH was introduced in a weight ratio of 1: 0 to 0: 1 in an amount of 5 mg / L. In similar conditions, a mixture of IOMS and EPPH in the claimed proportions is used.

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 braking coefficient was calculated by the formula

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

where K is the braking coefficient;

a _o - 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.

Example 2

In the circulating water of the “dirty” cycle (2) of the converter gas purification composition (mEq / l): Ca - 11.2; alkalinity - 9.5; iron (mg / l) - 0.5; suspended solids - 50,000; a pH of 10.2 was administered a composition of IOMS and AFPG in a mass ratio of 1: 0 to 0: 1 in an amount of 5 mg / L. In similar conditions, a mixture of IOMS and EPPH in the claimed proportions is used. 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 drag coefficient was calculated by the formula (1).

The data are presented in table.2.

From the data presented in Tables 1, 2, it can be seen that the use of a composition from an IOMS inhibitor and a polyethylene glycol phosphate ester with a mass ratio of IOMS: EPPH = 9: 1-7: 3 can significantly increase the effect of inhibition of corrosion as in slightly acidic (example 1), and alkaline environment (example 2). A change in the values of n and m in the EPPH molecule does not significantly affect the decrease in the value of corrosion. At a ratio of 5: 5 (1: 1), the effect of inhibition of the value of corrosion decreases to the value characteristic of EPPH, i.e. many times reduced.

In our opinion, the composition at IOMS: EPPH ratios of 9: 1-7: 3 has a synergistic effect, largely due to the dispersing properties of EPPG, which allows you to create a uniform monodisperse film of calcium complexonates of IOMS reagent, which helps to protect structural steel from corrosion.

Examples of inhibition of scaling in comparison with an analog or prototype.

Example 3

The effectiveness of the inhibition of scaling was tested in the waters of the above composition (1) according to Example 1. To evaluate the effectiveness of inhibiting the formation of calcium sulfate deposits, the proposed compositions in an amount of 3 mg / L were introduced into the test water. In order to intensify the formation of deposits, the water was heated in a water bath to a temperature of 80 ° C and kept at this temperature for 4 hours. The change in the calcium sulfate content in the solution after exposure was determined by the standard method using the complexometric method. The data are presented in table.3.

The inhibition efficiency was calculated by the formula

$$E\%=\frac{{\mathrm{FROM}}^{\mathrm{and}ng}-{\mathrm{FROM}}^{\mathrm{to}\mathrm{about}n}}{{\mathrm{FROM}}^{\mathrm{and}\mathrm{from}x}-{\mathrm{FROM}}^{\mathrm{to}\mathrm{about}n}}\times \mathrm{one\; hundred}\%,(2)$$

where C ^ing is the concentration of calcium sulfate after exposure in the presence of an inhibitor, g / l;

With ^con - the concentration of calcium sulfate in the control experiment after exposure, g / l;

With ^ref - the concentration of calcium sulfate before the experiment, g / l.

Example 4

To assess the effectiveness of inhibition of scaling of calcium carbonate in the circulating water of composition (2) according to example 2, the proposed composition was introduced in an amount of 5 mg / L. The effectiveness of the inhibition of calcium carbonate deposits was evaluated by the amount of calcium carbonate formed on the surface of the glass after exposure for 4 hours and a temperature of 70 ° C. To this end, the glasses were previously degreased and treated with a chromium mixture, washed with tap and distilled water. After exposure, the sediment from the walls was dissolved 0.1 N. hydrochloric acid solution, neutralized with alkali and calcium in the solution was determined by standard methods. The results were converted to calcium carbonate.

The data are presented in table 4.

The inhibition efficiency was calculated by the formula

$$E\%=\mathrm{one\; hundred}-\frac{m_{C\mathrm{but}}{}^{P\mathrm{about}\mathrm{from}le}}{m_{C\mathrm{but}}{}^{d\mathrm{about}}}\times \mathrm{one\; hundred}\%,(3)$$

where m _Ca ^to - the amount of calcium before exposure, mg;

m _Ca ^after - the amount of calcium after the end of the exposure, mg.

From the data presented in table 3.4, it can be seen that, as in the case of corrosion inhibition, the proposed composition in the IOMS: EPPH ratio also has a synergistic effect, preventing both crystallization of calcium sulfate (example 3) and the formation of deposits calcium carbonate (example 4).

In our opinion, the synergistic effect, on the one hand, is due to the adsorption of IOMS on the micronuclei of the crystallizing salt, and, on the other hand, due to the additionally dispersing effect of EPPH.

Example 5

Into the water of the “dirty” reverse cycle of the steelmaking production composition (mg / l): Ca ²⁺ - 1400; sulfates - 2700; Fe ²⁺ - 10; petroleum products - 0.4; chlorides - 150; fluorides - 50; pH 4.5; suspended solids - 22000 (22 g / l) were administered compositions from OEDPK and EPPG with mass ratios OEDPK: EPPG = 9: 1-7: 3 in the amount of 10 mg / L. The corrosion rate was evaluated at a temperature of 20 ° C with an Expert-004 corrosion meter.

The data are presented in table.5.

Example 6

In the circulating water of the "dirty" cycle of the converter gas purification composition (mEq / l): Ca - 11.2; alkalinity - 9.5; iron (mg / l) - 0.5; suspended solids - 50,000; A pH of 10.2 introduced a composition of OEDPK and AFPG in a weight ratio of 9: 1 to 7: 3 in an amount of 5 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 with an Expert-004 corrosion meter.

The data are presented in table.6.

From the data presented in Tables 5 and 6, it can be seen that the use of a composition from an HEDPA inhibitor and phosphate ester of polyethylene glycol at a weight ratio of HEDPA: EPPH = 9: 1-7: 3 allows to increase the effect of inhibition of corrosion in both slightly acidic (example 5), so and alkaline environment (example 6). At a ratio of 5: 5 (1: 1), the effect of inhibition of the value of corrosion decreases to the value characteristic of EPPH, i.e. decreases.

Example 7

The effectiveness of the inhibition of scaling was tested on the waters of the above composition according to example 5. To assess the effectiveness of inhibition of the formation of calcium sulfate deposits, the OEDPC and EPPH compositions in an amount of 3 mg / L were introduced into the test water. In order to intensify the process of formation of deposits, water was heated in a water bath to a temperature of 80 ° C and kept at this temperature for 4 hours. The change in the calcium sulfate content in the solution after exposure was determined by the standard method using the complexometric method. The data are presented in table.7.

Example 8

To assess the effectiveness of the inhibition of scaling of calcium carbonate in the circulating water of the composition according to example 6, the composition of HEDPA and EPPH was introduced in an amount of 5 mg / L. The effectiveness of the inhibition of deposits of calcium carbonate was evaluated by the amount of calcium carbonate formed on the surface of the glass after exposure for 4 hours and a temperature of 70 ° C. To this end, the glasses were previously degreased and treated with a chromium mixture, washed with tap and distilled water. After exposure, the sediment from the walls was dissolved 0.1 N. hydrochloric acid solution, neutralized with alkali and calcium in the solution was determined by standard methods. The results were converted to calcium carbonate.

The data are presented in table.8.

From the data presented in tables 7, 8, it can be seen that, as in the case of corrosion inhibition, the HEDPK: EPPH composition also has a synergistic effect, preventing both crystallization of calcium sulfate (example 7) and the formation of calcium carbonate deposits ( example 8).

Example 9

Into the water of the "dirty" reverse cycle of steelmaking production composition (mg / l): Ca ²⁺ - 1400; sulfates - 2700; Fe ³⁺ - 10; petroleum products - 0.4; chlorides - 150; fluorides - 50; pH 4.5; suspended solids - 22000 (22 g / l) were administered compositions from PAF-13 and EFPH in mass ratios. PAP-13: EFP = 9: 1-7: 3 in an amount of 10 mg / L. The corrosion rate was evaluated at a temperature of 20 ° C with an Expert-004 corrosion meter.

The data are presented in table.9.

Example 10

In the circulating water of the "dirty" cycle of the converter gas purification composition (mEq / l): Ca - 11.2; alkalinity - 9.5; iron (mg / l) - 0.5; suspended solids - 50,000; A pH of 10.2 introduced a composition of PAF-13 and EFPH in a weight ratio of 9: 1 to 7: 3 in an amount of 5 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 with an Expert-004 corrosion meter.

The data are presented in table 10.

The data presented in Tables 9, 10 show that the use of a composition of a PAF-13 inhibitor and phosphate ester of polyethylene glycol with a mass ratio of PAF-13: EPPH = 9: 1-7: 3 allows to increase the effect of inhibition of the value of corrosion as in slightly acidic (example 9) and alkaline environment (example 10). At a ratio of 5: 5 (1: 1), the effect of inhibition of the value of corrosion decreases to the value characteristic of EPPH, i.e. decreases.

Example 11

The effectiveness of the inhibition of scaling was tested in the waters of the above composition according to example 5. To assess the effectiveness of inhibition of the formation of calcium sulfate deposits, the PAF-13 and EPPH compositions in an amount of 3 mg / L were introduced into the test water. In order to intensify the process of formation of deposits, water was heated in a water bath to a temperature of 80 ° C and kept at this temperature for 4 hours. The change in the calcium sulfate content in the solution after exposure was determined by the standard method using the complexometric method. The data are presented in table.11.

Example 12

To assess the effectiveness of the inhibition of scaling of calcium carbonate in the circulating water of the composition according to example 6, the composition PAF-13 and EPPH was introduced in an amount of 5 mg / L. The effectiveness of the inhibition of deposits of calcium carbonate was evaluated by the amount of calcium carbonate formed on the surface of the glass after exposure for 4 hours and a temperature of 70 ° C. To this end, the glasses were previously degreased and treated with a chromium mixture, washed with tap and distilled water. After exposure, the sediment from the walls was dissolved 0.1 N. hydrochloric acid solution, neutralized with alkali and calcium in the solution was determined by standard methods. The results were converted to calcium carbonate.

The data are presented in table.12.

From the data presented in tables 11, 12 it can be seen that, as in the case of corrosion inhibition, the composition PAF-13: EPPH also has a synergistic effect, preventing both crystallization of calcium sulfate (example 11) and the formation of calcium carbonate deposits (example 12).

From the data presented in tables 5-12, it is seen that OEDPK and PAF-13 in a composition with EPPH at the claimed ratios reduce the amount of corrosion and inhibit the crystallization process, compared with the prototype. However, it should be noted that OEDPK and PAF-13 in the composition with EPPH (examples No. 5-No. 12) in comparison with the IOMS reagent in the composition with EPPH (examples No. 1-No. 4) is less effective.

Table 1 Corrosion rate in a slightly acidic environment No. p / p Composition Mass ratio Corrosion rate, microns / year Braking coefficient one IOMS: EFG 1-0 342 0 (analog) 2 IOMS: EFG 0: 1 119 2.9 n is 5; m = 16 (prototype) 3 IOMS: EFG 0: 1 132 2.6 n is 12; m = 3 (prototype) four IOMS: EFG 0: 1 140 2,4 n is 12; m = 16 (prototype) 5 IOMS: EFG 9: 1 28 12,2 n is 5; m = 16 (according to the invention) 6 IOMS: EFG 9: 1 19 18.0 n is 12; m = 3 (according to the invention) 7 IOMS: EFG 9: 1 25 13.7 n is 12; m = 16 (according to the invention) 8 IOMS: EFG 7: 3 27 12.6 n is 5; m = 16 (according to the invention) 9 IOMS: EFG 7: 3 21 16.3 n is 12; m = 3 (according to the invention) 10 IOMS: EFG 7: 3 thirty 11,4 n is 12; m = 16 (according to the invention) eleven IOMS: EFG 5: 5 125 2.7 n is 5; m = 16 (according to the invention) 12 IOMS: EFG 5: 5 142 2,4 n is 12; m = 3 (according to the invention)

table 2 Alkaline corrosion rate No. p / p Composition Mass ratio Corrosion rate, microns / year Braking coefficient one IOMS: EFG 1-0 237 0 (analog) 2 IOMS: EFG 0: 1 118 2.0 n is 5; m = 16 (prototype) 3 IOMS.EFPG 0: 1 115 2.1 n = 12; m = 3 (prototype) four IOMS: EFG 0: 1 120 1.9 n = 12; m = 16 (prototype) 5 IOMS: EFG 9: 1 19 12.5 n is 5; m = 16 (according to the invention) 6 IOMS: EFG 9: 1 fifteen 15.8 n is 12; m = 3 (according to the invention) 7 IOMS: EFG 9: 1 fifteen 15.8 n is 12; m = 16 (according to the invention) 8 IOMS: EFG 7: 3 9 26.3 n is 5; m = 16 (according to the invention) 9 IOMS: EFG 7: 3 8 29.6 n is 12; m = 3 (according to the invention) 10 IOMS: EFG 7: 3 10 23.7 n is 12; m = 16 (according to the invention) eleven IOMS: EFG 5: 5 125 1.9 n is 12; m = 3 (according to the invention) 12 IOMS: EFG 5: 5 123 1.9 n is 12; m = 16 (according to the invention)

Table 3 Crystallization of calcium sulfate in a slightly acidic environment No. p / p Composition Mass ratio The concentration of calcium sulfate in solution, g / l Efficiency% one The control - 2.2 0,0 2 IOMS: EFG 1-0 2,5 27.3 (analog) 3 IOMS: EFG 0: 1 2.6 36,4 n is 5; m = 15 (prototype) four IOMS: EFG 0: 1 2.6 36,4 n is 12; m = 3 (prototype) 5 IOMS: EFG 0: 1 2.6 36,4 n is 12; m = 16 (prototype) 6 IOMS: EFG 9: 1 3.2 90.9 n is 5; m = 16 (according to the invention) 7 IOMS: EFG 9: 1 3.2 90.9 n = 12; m = 16 (according to the invention) 8 IOMS: EFG 7: 3 3.3 100.0 n is 12; m = 3 (according to the invention) 9 IOMS: EFG 7: 3 3.3 100.0 n is 12; m = 16 (according to the invention) 10 IOMS: EFG 5: 5 2.6 36,4 n is 5; m = 16 (according to the invention) eleven IOMS: EFG 5: 5 2.6 36,4 n is 12; m = 16 (according to the invention)

Table 4 Crystallization of calcium carbonate in an alkaline environment No. p / p Composition Mass ratio The amount of calcium carbonate, mg Efficiency% one The control - 21 0,0 2 IOMS: EFG 1-0 12.7 39.5 (analog) 3 IOMS: EFG 0: 1 10.3 50.9 n is 3; m = 16 (prototype) four IOMS: EFG 0: 1 10.8 48.6 n is 12; m = 3 (prototype) 5 IOMS: EFG 9: 1 0.6 97.1 n is 5; m = 16 (according to the invention) 6 IOMS: EFG 9: 1 0.5 97.6 n is 12; m = 3 (according to the invention) 7 IOMS: EFG 9: 1 0.4 98.1 n is 12; m = 16 (according to the invention) 8 IOMS: EFG 7: 3 0.3 98.6 n is 5; m = 16 (according to the invention) 9 IOMS: EFG 7: 3 0.3 98.6 n is 12; m = 16 (according to the invention) 10 IOMS: EFG 5: 5 10.5 50,0 n is 8; m = 16 (according to the invention) eleven IOMS: EFG 5: 5 10.9 48.1 n is 12; m = 16 (according to the invention)

Table 5 Corrosion rate in a slightly acidic environment No. p / p Composition Mass ratio Corrosion rate, microns / year Braking coefficient one OEDFK: EFPG 0: 1 132 2.6 n = 12 m = 13 (prototype) 2 OEDFK: EFPG 9: 1 108 3.2 n = 12 m = 3 3 OEDFK: EFPG 7: 3 92 3,7 n = 12 m = 3 four OEDFK: EFPG 5: 5 140 2,4 n = 12 m = 3

Table 6 Alkaline corrosion rate No. p / p Composition Mass ratio Corrosion rate, microns / year Braking coefficient one OEDFK: EFPG 0: 1 118 2.0 n = 12; m = 13 (prototype) 2 OEDFK: EFPG 9: 1 75 3.2 n = 12 m = 3 3 OEDFK: EFPG 7: 3 64 3,7 n = 12 m = 3 four OEDFK: EFPG 5: 5 128 1.8 n = 12 m = 3

Table 7 Crystallization of calcium sulfate in a slightly acidic environment No. p / p Composition Mass ratio The concentration of calcium sulfate in solution, g / l Efficiency% one The control - 2.2 0,0 2 OEDFK: EFPG 1-0 2,5 27.3 [analogue) 3 OEDFK: EFPG 0: 1 2.6 36,4 n is 12; m = 3 (prototype) four OEDFK: EFPG 9: 1 2.7 45.4 n = 12 m = 3 5 OEDFK: EFPG 7: 3 2,8 54.5 n = 12 m = 3 6 OEDFK: EFPG 5: 5 2,5 27.3 n = 12 m = 3

Table 8 Crystallization of calcium carbonate in an alkaline environment No. p / p Composition Mass ratio The amount of calcium carbonate, mg Efficiency% one The control - 21 0,0 2 OEDFK: EFPG 1-0 15.7 25,2 (analog) 3 OEDFK: EFPG 0: 1 10.3 50.9 n = 12 m = 3 four OEDFK: EFPG 9: 1 3.8 81.9 n = 12 m = 3 5 OEDFK: EFPG 7: 3 3.6 82.8 n = 12 m = 3 6 OEDFK: EFPG 5: 5 10.5 50,0 n = 12 m = 3

Table 9 Corrosion rate in a slightly acidic environment No. p / p Composition Mass ratio Corrosion rate, microns / year Braking coefficient one PAF-13: EFP 0: 1 132 2.6 n = 12 m = 13 (prototype) 2 PAF-13: EFP 9: 1 41 8.4 n = 12 m = 3 3 PAF-13: EFP 7: 3 34 10.1 n = 12 m = 3 four PAF-13: EFP 5: 5 136 2,5 n = 12 m = 3

Table 10 Alkaline corrosion rate No. Composition Mass ratio Corrosion rate, microns / year Braking coefficient one PAF-13: EFP 0: 1 118 2.0 n = 12 m = 13 (prototype) 2 PAF-13: EFP 9: 1 55 4.3 n = 12 m = 3 3 PAF-13: EFP 7: 3 34 6.9 n = 12 m = 3 four PAF-13: EFP 5: 5 123 1.9 n = 12 m = 3

Table 11 Crystallization of calcium sulfate in a slightly acidic environment No. p / p Composition Mass ratio The concentration of calcium sulfate in solution, g / l Efficiency% one The control - 2.2 0,0 2 PAF-13: EFP 1-0 2,5 27.3 (analog) 3 PAF-13: EFP 0: 1 2.6 36,4 n is 12; m = 3 (prototype) four PAF-13: EFP 9: 1 3.0 72.7 n = 12 m = 3 5 PAF-13: EFP 7: 3 3,1 8,1,8 n = 12 m = 3 6 PAF-13: EFP 5: 5 2.6 36,4 n = 12 m = 3

Table 12 Crystallization of calcium carbonate in an alkaline environment No. p / p Composition Mass ratio The amount of calcium carbonate, mg Efficiency% one The control - 21 0,0 2 PAF-13: EFP 1-0 13.7 34.7 (analog) 3 PAF-13: EFP 0-1. 10.3 50.9 n = 12 m = 3 four PAF-13: EFP 9: 1 2,8 86.6 n = 12 m = 3 5 PAF-13: EFP 7: 3 2.6 87.6 n = 12 m = 3 6 PAF-13: EFP 5: 5 11.1 47.1 n = 12 m = 3

Claims (2)

1. A method of preventing scaling and corrosion in water supply systems by introducing a mixture of a mineral scale inhibitor and polyethylene glycol phosphate ester into the treated water at a weight ratio of 9: 1-7: 3, 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.