RU2331591C1 - Composition for removing deposits and scum from inner surfaces of heat-exchange equipment - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention pertains to the chemical industry, heat energy, water supply and other fields of national economy, and specifically to compositions for removing deposits and scum from inner surfaces of pipes, heat-exchangers and technological apparatus. The proposed composition consists of sodium or potassium pyrosulphate, or ammonia, polypheonol compounds of wood or softwood bark, urotropin, non-ionic surfactant, hydrochloric acid, acetone and water with the following content of components in mass%: pyrosulphate of sodium or potassium or ammonia or persulphate of sodium or potassium or ammonia - 0.09-10, polyphenol compounds of wood or softwood bark 0.003-6.0, urotropin 0.01-4, non-ionic surfactant - 0.0015-0.1, hydrochloric acid - 2.0-24.0, acetone - 1.0-8.0, water constitutes the rest.

EFFECT: increased rate of dissolving of deposits and scum with retention of high degree of protection from corrosion.

1 tbl, 13 ex

Description

The invention relates to the chemical industry, heat power, water supply and other sectors of the economy, namely, compositions for removing deposits and scale from the inner surfaces of pipes, heat exchangers and process apparatuses.

A known composition for descaling (Patent RU No. 2085517), containing in wt.%: Potassium or sodium bisulfate or pyrosulfate 5-12, water - the rest. The composition may also contain hydrochloric and acetic acids in an amount of 4-8 and 4-6 wt.%, Respectively.

Closest to the invention in technical essence and the achieved effect is a composition for descaling (Patent RU No. 2257354), containing in wt.%: Sodium or potassium pyrosulfate, or ammonium or sodium sulphate or potassium, or ammonium - 0.09-10, 0, polyphenolic compounds of coniferous bark - 0.003-2.0, urotropin - 0.01-4.0, nonionic surfactant - 0.0015-0.009, polyhexamethylene guanidine chloride - 0.1-1.5, hydrochloric acid - 2.0 -15.0, water - the rest.

The scale and deposits on the internal surfaces of the heat exchange equipment contain, in addition to inorganic components interacting with various acids, a significant amount of organic impurities. The formation of such deposits and scale is associated with the ingress of machine oils into the water circulation system and biofouling. The most characteristic formation of such deposits and scale for industrial heat exchange equipment. Such deposits and scale have hydrophobic properties, which prevents their interaction with the compositions to remove scale and water-based deposits.

The aforementioned descaling compositions have a low penetrating ability deep into the iron oxide deposits and scale, which requires a significant increase in contact time, leading to both an increase in cleaning time and chemical corrosion of the internal surfaces of heat exchange equipment, and a decrease in cleaning efficiency. Therefore, the disadvantages of these compositions are the low dissolution rate of scale and deposits containing machine oils or biofouling products, the low dissolution rate of iron oxide deposits and scale, and the high corrosivity of the compositions to metal surfaces.

To eliminate these drawbacks: reduce chemical corrosion, increase the dissolution rate of iron oxide deposits and increase the dissolution rate of scale and deposits containing machine oils and biofouling products, the composition is proposed (wt.%):

Sodium or potassium pyrosulfate, or ammonium or persulfate sodium or potassium or ammonium 0.09-10 Polyphenolic compounds of wood or bark conifers 0.003-6.0 Urotropin 0.01-4 Nonionic surfactant 0.0015-0.1 Hydrochloric acid- 2.0-24.0 Acetone 1.0-8.0 Water - rest.

Example No. 1. Composition containing in wt.%: Hydrochloric acid 4.0 and nonionic surfactant 0.002.

The tests are carried out for corrosion activity, the dissolution rate of scale containing organic oils, and the dissolution rate of iron oxide deposits.

For each test, a composition with a volume of 200 ml is taken, heated in a thermostat to a temperature of 40 ° C, after which the test sample is placed in it.

To study the corrosion activity of the composition on the metal, samples of plates from Steel 3 are used, which are degreased beforehand, dried at a temperature of 110 ° C and cooled to room temperature. Tests for the corrosion activity of the compositions for removing deposits and scale from the inner surfaces of the heat exchange equipment are as follows. Metal plates with the same surface are weighed on an analytical balance with an accuracy of 4 decimal places. After weighing, the samples are soaked in the test composition to remove scale and deposits at a temperature of 40 ° C and a contact time of 4 hours. At the end of the experiment, metal samples are removed, washed in running water, dried, cooled and weighed. Analysis of the results is carried out based on the difference in mass of the samples before and after processing them in the studied compounds.

The dissolution rate of scale containing organic oils is measured by the weight loss of the bars consisting of CaO: CaSO ₄ = 34: 66 (obtained by mixing 34% lime and 66% gypsum) measuring 15 × 15 × 50 mm and impregnated with transformer oil at 80 ° C . A bar sample is weighed on an analytical balance with an accuracy of 4 decimal places. After weighing, the sample is soaked in the test composition to remove scale and deposits for 2 hours. At the end of the experiment, the sample is removed from the solution, washed in running water, dried at a temperature of 100 ° C, cooled to room temperature and weighed. Analysis of the results is carried out based on the difference in mass of the sample before and after processing it in the test solution.

The dissolution rate of iron oxide deposits and scale is estimated by increasing the number of iron (III) ions in the solution. Determination of iron (III) is carried out by differential photocolorimetry, based on the formation of colored complex compounds of iron (III) ions with sulfosalicylic acid. The determination of iron (III) is carried out at a pH of 1.8-2.5 and a wavelength of 510 nm, which corresponds to the maximum absorption of the monosulfosalicylate complex.

As samples of iron oxide deposits, sawn along the pipe of hot water supply of the city of Irkutsk, which have been in operation for more than 20 years, with an internal diameter of 15 mm and a length of 50 mm, are used. Scale and deposits in the pipes contain in wt.% Calcium and magnesium carbonate - 6, iron oxide (III) - 83, biofouling products - 6, sand - 5.

Samples of metal pipes of the same length are soaked in the test composition to remove deposits and scale. The content of iron ions in the solution is determined after 4 hours.

Example No. 2. Composition containing in wt.%: Hydrochloric acid 4.0 and acetone 5.0. The tests are carried out under the conditions of example 1.

Example No. 3. Made in the conditions of the prototype. Composition containing (wt.%): Hydrochloric acid - 15, ammonium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, polyhexamethylene guanidine chloride - 1.5, nonionic surfactant - 0.0015, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 4. Composition containing (wt.%): Hydrochloric acid - 15, ammonium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, acetone - 1, nonionic surfactant - 0.0015, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 5. Composition containing (wt.%): Hydrochloric acid - 15, potassium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, acetone - 8, nonionic surfactant - 0.0015, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 6. Composition containing (wt.%): Hydrochloric acid - 15, sodium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, acetone - 10, nonionic surfactant - 0.0015, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 7. Composition containing (wt.%): Hydrochloric acid - 15, ammonium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, acetone - 5, nonionic surfactant - 0.0015, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 8. Composition containing (wt.%): Hydrochloric acid - 15, ammonium persulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, acetone - 5, nonionic surfactant - 0.0015, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 9. Composition containing (wt.%): Hydrochloric acid - 15, sodium persulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, acetone - 5, nonionic surfactant - 0.1, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 10. Composition containing (wt.%): Hydrochloric acid - 15, ammonium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, acetone - 5, nonionic surfactant - 0.5, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 11. Composition containing (wt.%): Hydrochloric acid - 24, ammonium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous bark - 1, acetone - 5, nonionic surfactant - 0.1, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 12. Composition containing (wt.%): Hydrochloric acid - 24, sodium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous wood - 1, acetone - 5, nonionic surfactant - 0.1, water - the rest. The tests are carried out in the conditions of example No. 1.

Example No. 13. Composition containing (wt.%): Hydrochloric acid - 30, ammonium pyrosulfate - 2, urotropin - 4, polyphenolic compounds of coniferous wood - 1, acetone - 5, nonionic surfactant - 0.1, water - the rest. The tests are carried out in the conditions of example No. 1.

Table 1.
Corrosion activity, the dissolution rate of scale containing organic oils, and the dissolution rate of iron oxide deposits for examples 1-13. Example No. The degree of corrosion protection relative to the composition shown in example 3,% The dissolution rate of oiled scale relative to the composition shown in example 3,% The dissolution rate of iron oxide deposits and scale relative to the composition shown in example 3,% one 5 81 53 2 17 93 91 3 one hundred one hundred one hundred four 115 131 125 5 134 170 140 6 135 178 142 7 129 153 135 8 128 154 136 9 136 195 147 10 136 199 147 eleven 120 175 161 12 123 175 162 13 89 181 162

The results of corrosion activity, the dissolution rate of scale containing organic oils, and the dissolution rate of iron oxide deposits of the examples are presented in table No. 1. As a benchmark for assessing the influence of the components of the composition on the degree of protection against corrosion, the dissolution rate of oily scale and the dissolution rate of iron oxide deposits and scale was chosen the composition of the prototype (example No. 3).

As can be seen from a comparison of the data (table 1) of example 1 and example 2, it follows that the introduction of acetone increases the degree of protection against corrosion. At the same time, an increase in the dissolution rate of oily scale and iron oxide deposits and scale is observed.

A comparison of the results presented in examples 1, 2 and 3 shows that the composition of the prototype is superior in terms of protection against corrosion, the dissolution rate of oily deposits and the dissolution rate of iron oxide deposits and scale hydrochloric acid with surfactant or acetone additives.

When comparing the results of examples 3 and 4, it is seen that the addition of acetone increases the degree of protection against corrosion and increases the dissolution of oily scale and iron oxide deposits and scale. Increasing the concentration of acetone (example 5) reduces the degree of corrosion, and also significantly increases the dissolution of oily scale and iron oxide deposits and scale. Increasing the acetone content to 10 wt.% (Example 6) does not affect the degree of protection against corrosion. In this case, the dissolution rate of oily scale and iron oxide deposits practically does not change. Therefore, a further increase in the acetone content in the proposed composition is impractical.

When comparing example 7 and example 8, it is seen that the replacement of ammonium pyrosulfate with ammonium persulfate does not affect the degree of corrosion and the dissolution rate of deposits and scale, which significantly expands the raw material base for obtaining compositions for removing deposits and scale.

When comparing the data of examples 5 and 7, it is seen that a decrease in the concentration of nonionic surfactant significantly reduces the dissolution rate of oily deposits and practically does not affect the degree of protection against corrosion and dissolution of iron oxide deposits. With an increase in the amount of nonionic surfactant (Example 9), an increase in the dissolution rate of oily deposits and the dissolution rate of iron oxide deposits and scale is observed. An increase in the amount of surfactant has practically no effect on the degree of protection against corrosion. A further increase in the amount of non-ionic surfactant presented in Example 10 has practically no effect on: the degree of corrosion protection, the dissolution rate of oily deposits and the dissolution rate of iron oxide deposits and scale. In this case, a significant foaming of the solution is observed, which complicates the work with the composition.

When comparing the data of examples 4, 5, 7, 9 with example 11, it is seen that an increase in the acid content increases the dissolution rate of iron oxide deposits and scale, as well as oily deposits, however, there is a decrease in the degree of protection of the metal from corrosion. A further increase in the acid content (example 13) significantly reduces the degree of protection of the metal from corrosion. In this case, an increase in the acid content above 24% is impractical, since it is not completely consumed and additional costs are required to neutralize the spent solutions.

When comparing the dissolution rate of iron oxide deposits and the degree of metal protection against corrosion, presented in examples 11 and 12, it can be seen that it is possible to use not only polyphenolic compounds of coniferous bark, but also polyphenolic compounds of coniferous wood, which significantly expands the raw material base for obtaining compositions for removal of deposits and scale from the internal surfaces of heat exchange equipment.

The most optimal are given in examples 4, 5, 7, 8, 9, 11, 12, the concentration of the components in wt.%: Sodium or potassium pyrosulfate, or ammonium or sodium or potassium persulfate, or ammonium - 0.09-10.0 , polyphenolic compounds of wood or coniferous bark - 0.003-6.0, urotropin - 0.01-4.0, nonionic surfactant - 0.0015-0.1, hydrochloric acid - 2.0-24.0, acetone - 1 , 0-8.0, water - the rest.

Claims (1)

Composition for removing deposits and scale from the inner surfaces of heat exchange equipment, consisting of sodium pyrosulphate, or potassium, or ammonium, polyphenolic compounds of coniferous bark, urotropin, nonionic surfactant, hydrochloric acid and water, characterized in that the composition additionally contains acetone, as polyphenolic compounds may contain polyphenolic compounds of coniferous wood, and instead of potassium, sodium or ammonium pyrosulfate may contain potassium, sodium or ammonium persulfate in the following ratio and components, wt.%: Sodium pyrosulfate, or potassium, or ammonium or sodium or potassium persulfate, or ammonium 0.09-10 Polyphenolic compounds of wood or bark conifers 0.003-6.0 Urotropin 0.01-4 Nonionic surfactant 0.0015-0.1 Hydrochloric acid 2.0-24.0 Acetone 1.0-8.0 Water Rest