RU2303084C1 - Composition for protection of water supply and water disposal systems against corrosion and deposit of salts - Google Patents

Abstract

FIELD: devices for protection against corrosion and deposition of salts, mainly scale, of water supply and water disposal systems.

SUBSTANCE: proposed composition contains the following components, mass-%: phosphoric acid (in terms of 100-% acid),0.01-74; calcium oxide or calcium hydroxide, or calcium carbonate or mixture of them (in terms of calcium oxide), 5-25; magnesium oxide or magnesium hydroxide, or magnesium carbonate, or mixture of them (in terms of magnesium oxide), 0.45-5; potassium hydroxide or potassium carbonate or mixture of them (in terms of potassium oxide), 0.01-5; silicon dioxide or water glass (in terms of silicon dioxide),0.2-2.2; sodium phosphates of common formula xNa₂OyP₂O₅zH₂O at molar ratio of (Na₂O+H₂O)/P₂O₅ from 1 to 3 (in terms of sodium oxide), 8-75; magnesium oxides of common formula Mn_xO_y at molar ratio Mn/O from 1 to 2 (in terms of magnesium), 0.01-0.3.

EFFECT: enhanced ecological safety; improved anti-corrosion and anti-scale properties; improved quality of water due to deceleration of eutrophication process.

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Description

The invention relates to means for protecting equipment from corrosion and scaling, mainly scale, and can be used in domestic and industrial water supply networks, as well as water disposal.

A known composition for protecting against corrosion of the surface of iron and mild steel, containing phosphoric acid in an amount of 66.7 wt.% And sodium hexametaphosphate in an amount of 33.3 wt.% (See US patent No. 4105406, C09K 15/02, C23F 11 / eighteen).

The disadvantages of the known composition are low anticorrosion properties due to the fact that a thin phosphate film formed on a metal surface has low hydrophobic properties due to the high solubility of its components in water, as well as low anti-scale properties due to the impossibility of creating hardness salts in microcrystals in water , an adsorption film, as a result of which coalescence of small particles of hardness salts into large ones, which are deposited in a thick layer in the form of scale on the surface of water systems supply.

In addition, the known composition contributes to the activation of the process of eutrophication of water due to the fact that the components of the composition, having high solubility, saturate water with high concentration phosphates, which are the basis for the "flowering" of water and the appearance of a putrid odor.

The closest analogue to the claimed object is a composition for protection against corrosion and scaling of water supply systems containing phosphoric acid, sodium hydroxide or sodium carbonate, or a mixture thereof, magnesium oxide or magnesium hydroxide, or magnesium carbonate, or a mixture thereof, potassium hydroxide or potassium carbonate , or a mixture thereof, silicon dioxide, or equivalent glass in the following ratio of components, wt.%:

Phosphoric acid 66.5-72.0 Sodium hydroxide or sodium carbonate, or their mixture (in terms of sodium oxide) 14.5-19.5 Calcium oxide or calcium hydroxide, or carbonate calcium, or a mixture thereof (in terms of calcium oxide) 6.5-9.5 Magnesium Oxide or Magnesium Hydroxide, or Carbonate magnesium, or a mixture thereof (in terms of magnesium oxide) 0.9-3.0 Potassium hydroxide or potassium carbonate or their mixture (in terms of potassium oskide) 0.9-3.7 Silica or soluble glass (in terms of silicon dioxide) 0.8-2.2

(see RF patent No. 2149219, MKI C 23 F 11/00, 14/02).

Although the known composition is environmentally friendly, it nevertheless has low anticorrosive and anti-scale properties due to the inhomogeneous structure of the composition, as a result of which the phosphate film formed on the inner surface of water supply systems has low strength and hydrophobicity. In addition, the known composition does not provide a braking process for eutrophication of water due to the fact that the protective phosphate film formed not only on the surface of water supply systems, but also on the surface of water microflora, quickly loses its continuity due to the partial hydrolysis of readily soluble sodium and potassium components and thereby does not interfere with the access of oxygen to the microflora of water, which leads to its active reproduction, accompanied by flowering of water and the appearance of a putrefactive odor.

The basis of the invention is the task of developing an environmentally friendly composition, which, at a low concentration in water, simultaneously with high anti-corrosion and anti-scale protection of water supply and sanitation systems, would provide an increase in water quality by inhibiting the process of eutrophication of water.

The problem is solved in that the known composition for protection against corrosion and scaling of water supply and sanitation systems, containing phosphoric acid, calcium oxide or calcium hydroxide, or calcium carbonate, or a mixture thereof, silicon dioxide or soluble glass, according to the invention additionally contains sodium phosphates total formulas xNa ₂ O · yP ₂ O ₅ · zH ₂ O at a molar ratio (Na ₂ O + H ₂ O) / P ₂ O ₅ of one to three, manganese oxides of the general formula Mn _x O _y at a molar ratio of Mn / O from one to two with the following ratios of components, m ac%:

Phosphoric acid (in terms of 100%) 0.01-74 Calcium oxide or calcium hydroxide, or calcium carbonate, or their mixture (in terms of calcium oxide) 5-25 Magnesium oxide or magnesium hydroxide, or magnesium carbonate, or a mixture thereof (in terms of on magnesium oxide) 0.45-5 Potassium hydroxide or potassium carbonate, or a mixture thereof (in terms of potassium oxide) 0.01-5 Silica or soluble glass (in terms of silicon dioxide) 0.02-2.2 Sodium phosphates of the general formula xNa ₂ O · yP ₂ O ₅ · zH ₂ O when the molar ratio (Na ₂ O + H ₂ O) / P ₂ O ₅ from 1 to 3 (in terms of sodium oxide) 8-75 Manganese oxides of the general formula Mn _x O _y with a molar ratio of Mn / O from 1 to 2 (in terms of manganese) 0.01-0.3

The inventive composition for protection against corrosion and scaling of water supply and sanitation systems is prepared as follows.

Pre-dry components of the composition are crushed to a finely divided fraction with particle sizes of not more than 1 mm. After which the components taken in the claimed amount are thoroughly mixed until a dry, homogeneous mass is formed. Then, phosphoric acid is added to it in small portions with constant stirring of the resulting mixture, which is then kept at room temperature for at least 24 hours to ensure that preliminary chemical processes occur. After that, the obtained hard-plastic or brittle intermediate is melted at a temperature not exceeding 900 ° C until a homogeneous easily moving liquid mass is obtained and the latter is kept at a melting temperature of at least 30 minutes with periodic stirring. Then the liquid mass is poured into molds and cooled to form transparent glassy granules of various shapes, depending on the specific application conditions, for example, in the form of spheres, cylinders, pieces, etc.

Thus prepared granules of the composition are prepared for use in hot and cold water supply systems, as well as in drainage systems.

The shelf life of the granules of the claimed composition in a dry room is not limited.

To substantiate the advantages of the claimed composition compared with the composition taken as a prototype, tests were conducted in laboratory conditions.

Nine formulations were prepared using the above technology, including: six formulations of the composition with the claimed ratio of components (formulations 1-6); two compositions - with a ratio of components that go beyond the claimed limits (compositions 7 and 8) and one composition of the composition taken as a prototype (composition 9). The indicated compositions are shown in table 1.

The compositions for the protection of water supply and sanitation are given in table. one

Table 1 Components Composition Number one 2 3 four 5 6 7 8 9 Declared Prototype The content of components, wt.% one 2 3 four 5 6 7 8 9 10 Phosphoric Acid (100%) 0.01 20,0 24.5 38.6 54.5 72.0 73.0 0.01 69.25 Calcium oxide or calcium hydroxide, or calcium carbonate, or a mixture thereof (in terms of calcium oxide) 20,0 12.0 5,0 15.0 25.0 5,0 17.0 12.5 8.0 Magnesium oxide or magnesium hydroxide, or magnesium carbonate, or a mixture thereof (in terms of magnesium oxide) 4.0 3.0 0.45 2.75 5,0 0.5 0.001 5.5 1.95 Potassium hydroxide or potassium carbonate, or a mixture thereof (in terms of potassium oxide) 0.95 3.0 0.01 2,5 5,0 3.0 0.001 5.65 2,3 Silicon dioxide or soluble glass (in terms of silicon dioxide) 0,03 1.8 0.02 1,0 2.2 0.4 3,5 0.001 1,5 Sodium phosphates of the general formula xNa ₂ O · yP ₂ O ₅ · zH ₂ O at a molar ratio (Na ₂ O + H ₂ O) / P ₂ O ₅ of 1 to 3 (in terms of sodium oxide) 75.0 60.0 70.0 40,0 8.0 17.0 7.0 76.0 - Manganese oxides of the general formula Mn _x O _y with a molar ratio M _n / O from 1 to 2 (in terms of manganese) 0.01 0.2 0.02 0.15 0.30 0.1 0.001 0.348 - Sodium hydroxide or sodium carbonate, or a mixture thereof (in terms of sodium oxide) - - - - - - - 17.0

The environmental safety of each composition was determined by the value of the hydrogen index (pH) of an aqueous solution saturated at room temperature. The results are shown in table 2.

The values of hydrogen indicators (pH) of saturated aqueous solutions of the composition

table 2 Hydrogen indicator Composition Number Declared Prototype one 2 3 four 5 6 7 8 9 pH 6.3 8.5 8.0 8.5 7.0 6.1 5.5 9.5 7.3

Analysis of the results shown in table 2, allows us to conclude that the claimed compositions of the composition (compositions 1-6) are environmentally friendly, as well as the composition is a prototype (composition 9), since they correspond to the maximum permissible values of 6≤pN≤9 sanitary-hygienic standards of fire-drinking water.

The compositions 7 and 8 are not suitable for use in water supply and sanitation systems according to acceptable sanitary standards, since the pH of composition 7 is 5.5, that is, below the maximum permissible value due to excess of the acid component, and the pH of composition 8 is 9.5 , that is, above the maximum permissible value due to the excess of the main components of the composition.

To substantiate the increase in the anti-corrosion and anti-scale properties of the claimed composition compared to the prototype composition, five aqueous solutions of different concentrations of each composition composition were prepared (formulations 1-9, table 3). The study was also subjected to water, untreated compositions (composition 10, table 3).

Aqueous solutions of compositions 1-9 and water without treatment (composition 10) were heated to a temperature of 60 ± 1 ° C, which corresponds to the temperature of hot water supplied to the hot water supply system. In this case, the water heating temperature was chosen taking into account its higher aggressiveness to the pipeline in comparison with cold water.

Anticorrosive and anti-scale properties of the studied compositions

Table 3 Composition Number The concentration of the composition in water, mg / DM ³ The corrosion rate, mg / cm ² Scale layer thickness after testing, mm The content of hardness salts in the scale layer (in terms of CaO),% one 2 3 four 5 The claimed composition one 1,0 0,060 0.32 7.0 2.0 0.051 0.28 8.0 5,0 0,049 0.22 6.0 10.0 0,036 0.20 6.0 20,0 0,026 0.24 4.0 2 1,0 0,061 0.41 9.0 2.0 0.058 0.28 8.0 5,0 0,053 0.26 7.0 10.0 0,036 0.20 6.0 20,0 0,022 0.19 5,0 3 1,0 0,075 0.33 9.0 2.0 0,060 0.32 6.0 5,0 0.051 0.28 7.0 10.0 0,036 0.24 6.0 20,0 0.019 0.22 4.0 four 1,0 0,053 0.30 10.0 2.0 0,052 0.27 8.0 5,0 0,046 0.28 6.0 10.0 0,034 0.20 6.0 20,0 0,020 0.15 5,0 The claimed composition 5 1,0 0.056 0.36 8.0 2.0 0.051 0.37 7.0 5,0 0,047 0.26 7.0 10.0 0,032 0.25 5,0 20,0 0,021 0.21 3.0 6 1,0 0,057 0.30 7.0 2.0 0,050 0.25 6.0 5,0 0,044 0.23 6.0 10.0 0,030 0.24 5,0 20,0 0,023 0.18 4.0 7 1,0 0,110 0.80 16,4 2.0 0.104 0.78 15.8 5,0 0,098 0.79 15.7 10.0 0,094 0.64 14.9 20,0 0,091 0.68 13.9 8 1,0 0.106 1.00 19,4 2.0 0.107 0.95 18.8 5,0 0.103 0.84 18.3 10.0 0,090 0.80 17.0 20,0 0,087 0.74 17,2 Prototype 9 1,0 0,085 0.60 14.0 2.0 0,081 0.55 15.0 5,0 0,082 0.60 13.0 10.0 0,071 0.40 14.0 20,0 0,052 0.40 12.0 Water without treatment with the composition 10 - 0.30 2.0 76.0

Pieces of low-carbon steel pipes used in urban water supply systems were immersed in hot water.

To enhance the corrosion process by forming an galvanic pair, copper plates were connected to pipe sections. Using a magnetic stirrer, hot water was rotated, simulating the speed of water passing through a network pipeline. The test was carried out for 2 hours.

.The anticorrosion properties of the compositions (compositions 1–9) and untreated water (composition 10) were determined by the total mass of iron corrosion products that passed into the solution during the tests, as well as those taken from the pipe surface with a solution of hydrochloric acid with urotropine, which prevents the dissolution of metallic iron in acid. The corrosion rate was determined as the ratio of the mass of corroded iron per 1 cm ^{2 the} area of pipe segments

.

The test results shown in table 3 (column 3) show that the anticorrosion properties of the claimed composition (compositions 1-6) are 1.6-2.7 times higher than the anticorrosion properties of the prototype composition (composition 9) at the same concentrations in aqueous solutions and 4-15.8 times higher compared to untreated water (composition 10). To use compositions 7 and 8 for the treatment of water with a ratio of components that go beyond the declared limits, it is impractical, since their anticorrosion properties are deteriorating.

The study of the anti-scale properties of the compositions (formulations 1-10 of Table 3) was carried out on a pilot installation, the pipelines of which were made of carbon steel and corresponded in their technical characteristics to the pipelines of the city water supply and sanitation system. The pipelines of the pilot plant passed flows of water heated to a temperature of 60 ± 1 ° C of the Yangelskoe reservoir, which has a high content of hardness salts - up to 7 mol-eq / m ³ . At the same time, water treated through the inventive composition (compositions 1-8 of Table 3) was passed through the first pipeline, water treated by the prototype composition (composition 9 of Table 3) through the second pipeline, and water untreated by the compositions passed through the third pipeline (composition 10 tab. 3). The water flow rate in the pipelines was 1 l / min. After testing, pieces of pipes were cut from pipelines and the thickness of the layers of scale formed on the inner surfaces of the walls of the pipe sections was measured.

The test results are shown in column 4 of table 3. These results confirm the effectiveness of the use of the claimed composition for water treatment compared to the composition of the prototype. The thickness of the scale layer formed on the surface of the pipe through which water treated with the claimed composition (compositions 1-6, Table 3) passed is 1.5-2.7 times less than the thickness of the scale layer formed on the pipe through which water was passed treated with the composition of the prototype (composition 9, table 3), and 6-16.7 times less than the thickness of the scale layer formed during passage through the pipeline untreated water (composition 10, table 3).

The use of compositions 7 and 8 for the treatment of water is impractical due to a decrease in their anti-scale properties.

To determine the content of hardness salts in the composition of scale formed on the walls of the pipeline, the scale was treated with a solution of hydrochloric acid with urotropine. The content of hardness salts in the studied solutions was determined by the trilonometric method. The research results are shown in column 5 of table 3. These results are given in terms of calcium oxide.

From the results shown in column 5 of table 3, it can be seen that in the scale formed on the walls of the pipeline when water passed through it, treated with the claimed composition (compositions 1-6), the content of hardness salts is 1.4-4 times less than in scale formed by passing through the pipeline water treated with the composition of the prototype (composition 9), and 7.6-25 times less than the scale formed by passing through the pipeline untreated water (composition 10).

The test results of water treated with compounds 7 and 8 showed the inappropriateness of their use in water supply and sanitation systems due to the high corrosion rate (column 3, table 3) and an increase of about 2 times the thickness of the scale layer on the pipe surface (column 4, table .3), as well as a significant increase in the content of hardness salts in the composition of scale (column 5, Table 3). In this regard, the compositions of compositions 7 and 8 were excluded from subsequent studies.

To justify the expansion of the scope of the claimed composition in comparison with the prototype composition, experiments were carried out to determine the dissolution rate of compositions 1-6 and 9 (table 1) in water having the following desired temperature:

10 ° С - average temperature of natural water from underground sources;

25 ° С - room temperature of water;

60 ° С - average temperature of hot water in water supply and sanitation systems;

100 ° С - average water temperature in heating systems of residential premises.

For experiments, samples of the composition having the same shape, for example in the form of spheres or hemispheres, and approximately the same initial mass were selected. Samples were placed in water at a predetermined temperature maintained by thermostating method.

Daily, for 7 days, weighed samples of the composition taken out of the water. Then they were again placed in new portions of water with a given temperature. The test results are shown in table 4.

Solubility of compositions in water at different temperatures

Table 4 Composition Number The solubility of the composition, mg / DM ³ Water temperature, ° С 10 25 60 one hundred The claimed composition one 1,0 3.0 20,0 35.0 2 1,0 2.0 10.0 30,0 3 2.0 3,5 40,0 50,0 four 0.1 0.2 2.0 2,8 5 0.05 0.1 1,0 3.0 6 1,5 3.0 25.0 50,0 Prototype 9 3.0 5,0 50,0 100.0

According to the test results shown in table 4, we can conclude that, compared with the composition of the prototype (composition 9), the claimed compositions of compositions 1-6 can be used in a wide temperature range while maintaining controlled solubility:

- the compositions 1, 3, 6 have adjustable solubility up to 25 ° C and can be used to treat cold water supplied to the cold water supply system;

- compositions 2 and 5 can be used to treat water supplied both to the hot water supply and wastewater systems, and to the heat supply system;

- the composition of composition 2 maintains adjustable solubility up to 60 ° C and can be used for the treatment of cold and hot water.

Thus, the claimed composition, being environmentally safe in the content of phosphates, has a wide spectrum of action, as it provides controlled solubility in water, which, depending on the conditions of use, has a wide temperature range from 10 ° C to 100 ° C.

The composition 9 of the composition of the prototype can only process water having a temperature not higher than 25 ° C, since it is up to this temperature that the composition has controlled solubility, and at a temperature of water exceeding 25 ° C, the solubility of the composition becomes unregulated. This will lead to the fact that in hot water the phosphate content will significantly exceed the maximum permissible sanitary standards.

To justify the improvement of the quality of the treated water by reducing the speed of the eutrophication process, the following tests were carried out.

From the Verkhneuralskoye reservoir, in the shallow coastal zones of which water bloom is observed in the hot season, 3 water samples were taken before algae bloom:

- the first water sample is a control;

- the second sample of water - with the addition of the composition of the prototype in the amount of 5 mg / DM ³ ;

- a third sample of water - with the addition of the claimed composition in an amount of 5 mg / DM ³ .

Open containers with the indicated water samples were installed on the illuminated south side of the room, the temperature in which was almost constant at about 25 ° C.

Observation of water samples was carried out until the first signs of the appearance of greenish mucous formations, which was accompanied by the simultaneous appearance of an unpleasant putrefactive odor in water.

The test results showed:

- in the first control water sample, after 7 days there was an active “bloom” in the form of mucous flocculent and filamentous algae both in the entire volume of water, so on the walls and bottom of the tank, while the water had a persistent putrefactive odor;

- “blooming” of the 2nd water sample treated with the prototype composition began after 10 days and appeared in the form of a thick greenish coating on the walls and bottom of the tank, while the water had a faint putrid smell;

- in the 3rd sample of water treated with the claimed composition, on the 30th day from the beginning of the tests, a weak “bloom” of water was observed in the form of a light greenish bloom at the bottom of the tank.

At the same time, there was no putrid odor in the water.

Experiments with chlorinated tap water were also carried out using the method described above. The results of the experiments confirmed the inhibition of the eutrophication process in water treated with the claimed composition, which allows us to conclude that the water quality is improved. So, the beginning of the "bloom" of chlorinated tap water treated with the claimed composition was observed after 109 days, in the water treated with the prototype composition after 25 days, and in the control water sample after 13 days.

Based on the foregoing, we can conclude that the claimed composition for protection against corrosion and scaling of water supply and sanitation systems is efficient and eliminates the disadvantages that occur in the prototype, which is confirmed by examples of specific performance. Accordingly, the claimed composition composition can be used in networks of domestic and industrial water supply and sanitation, as well as heat supply and, therefore, meets the condition of "industrial feasibility".

Claims (1)

Composition for protection against corrosion and scaling of water supply and sanitation systems, containing phosphoric acid, calcium oxide, or calcium hydroxide, or calcium carbonate, or a mixture thereof, magnesium oxide or magnesium hydroxide, or magnesium carbonate, or a mixture thereof, potassium hydroxide, or carbonate potassium, or a mixture thereof, silicon dioxide or soluble glass, characterized in that it additionally contains sodium phosphates of the general formula xNa ₂ · O · yP ₂ O ₅ · zH ₂ O at a molar ratio (Na ₂ O + H ₂ O) / P ₂ O ₅ from one to three, manganese oxides of the general formula Mn _x O _y when mol the ratio of Mn / O from one to two in the following ratios of components, wt.%: Phosphoric acid (in terms of 100%) 0.01-74 Calcium oxide or calcium hydroxide or carbonate calcium, or a mixture thereof (in terms of calcium oxide) 5-25 Magnesium oxide, or magnesium hydroxide, or magnesium carbonate, or a mixture thereof (in terms of magnesium oxide) 0.45-5 Potassium hydroxide, or potassium carbonate, or a mixture thereof (in terms of potassium oxide) 0.01-5 Silica or soluble glass (in terms of silicon dioxide) 0.02-2.2 Sodium phosphates of the general formula xNa ₂ · O · yP ₂ O ₅ · zH ₂ O when the molar ratio (Na ₂ O + H ₂ O): P ₂ O ₅ from 1 to 3 (in terms of sodium oxide) 8-75 Manganese oxides of the general formula Mn _x O _y with a molar ratio of Mn: O from 1 to 2 (in terms of manganese) 0.01-0.3