RU2238915C1 - Descaling composition - Google Patents

Abstract

FIELD: industrial equipment scaling control.

SUBSTANCE: invention relates to petrochemical and chemical industries, power engineering, etc. and, in particular, to compositions eliminating scale from surfaces of pipes, heat-exchanges, and process apparatuses. Water-based descaling composition contains 0.09 to 10% inorganic substance selected from sodium, potassium, and ammonium persulfate, sodium, potassium, and ammonium persulfite; 2.0 to 8.0% aqueous hydrochloric acid; 0.0015-0.009% surfactant; and additionally, as corrosion inhibitors, 0.003-2% larch-origin polyphenolic compounds and 0.01-4% urotropin.

EFFECT: widened choice of descaling agents.

1 tbl, 6 ex

Description

The invention relates to the petrochemical, chemical industry, power system, water supply and other sectors of the national economy, and in particular to compositions for descaling the surface of pipes, heat exchangers and technological apparatuses.

A known composition for descaling, including, wt.%: Bischofite 39.3-52.0; acetic acid 1.0-3.0; water - the rest (Application RU No. 94013163).

The closest to the invention in technical essence and the achieved effect is a composition (Patent RU No. 2085517), containing, wt.%: Potassium or sodium bisulfate or persulfate 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.

The disadvantages of these compositions is their high corrosiveness to metal surfaces, as well as the low rate of dissolution of scale.

To eliminate these disadvantages, a composition is proposed that reduces the corrosion rate and increases the rate of dissolution of scale (wt.%):

Sodium pyrosulfate, or

potassium or ammonium or

sodium sulphate,

or potassium or ammonium 0.09-10

Polyphenol compounds

larch trees 0.003-2

Urotropin 0.01-4

Surfactant 0,0015-0,009

HCl 2.0-8.0

Water Else

Example 1. In a composition containing (wt.%): Sodium pyrosulfate 0.09; polyphenolic compounds of larch 2; urotropin 4; Surfactant 0,0015; HCl 8.0; water - the rest, prepared metal samples were placed, previously defatted and dried at a temperature of 110 ° C, cooled to room temperature. Tests for the corrosion activity of solutions of scale converters were carried out as follows. Metal samples with the same surface were weighed on an analytical balance with an accuracy of 4 decimal places. After weighing, the samples were soaked in the test solution of the scale converter. At the end of the experiment, metal samples were removed from solutions, washed in running water, dried, cooled, and weighed. Analysis of the results was carried out based on the difference in the mass of the samples before and after processing them in the studied solutions.

The rate of dissolution of the scale was measured by the rate of decrease in the weight of the bar consisting of CaCO ₃ : Ca ₃ PO ₄ = 80: 20.

As a reference, a solution of the scale converter of the prototype was used (example 6). Under similar conditions, the compositions shown in the remaining examples were analyzed.

Example 2. In contrast to example 1, the composition with a content, wt.%: Ammonium pyrosulfate 10; polyphenolic compounds of larch 2; urotropin 0.01; Surfactant 0,0015; HCl 8.0; water is the rest.

Example 3. In contrast to example 1, the composition with the content, wt.%: Potassium sulphate 2; polyphenolic compounds of larch 0.5; urotropin 0.5; Surfactant 0,009; Hcl 5; water is the rest.

Example 4. In contrast to example 1, the composition with a content, wt.%: Ammonium pyrosulfate 10; polyphenolic compounds of larch 0.003; urotropin 0.01; Surfactant 0,0015; Hcl 2; water is the rest.

Example 5. In contrast to example 1, the composition with a content, wt.%: Ammonium pyrosulfate 11; polyphenolic compounds of larch 2,5; urotropin 4,5; Surfactant 0,009; Hcl 4; water is the rest.

Example 6. The composition presented in the prototype, with the content, wt.%: Sodium pyrosulfate 8; acetic acid 5; Hcl 6; water is the rest.

The results of corrosion tests of the above examples are presented in the table.

As can be seen from the data presented in the table, an increase in the content of corrosion inhibitors of urotropin and polyphenolic compounds of larch slows the rate of dissolution of scale (example 5). The decrease in their content increases corrosion (examples 2 and 3). In the absence of urotropine and polyphenolic compounds of larch (example 6), the highest value of corrosion is observed. An increase in the content of hydrochloric acid of more than 8 wt.% Is not economically feasible, since it is not completely consumed in the process of dissolving scale and requires additional costs aimed at neutralizing it in the spent solution, and a decrease in the content of hydrochloric acid is below 2.0 wt.% (Example 4) reduces the rate of dissolution of scale, which increases the surface treatment time.

The most optimal are given in examples 1, 2, 3 and 4 of the concentration of the ingredients of the composition: sodium pyrosulfate, or potassium, or ammonium or sodium sulphate, or potassium, or ammonium 0.09-10 wt.%, Polyphenolic compounds of larch 0.003-2 wt. %, urotropin 0.01-4 wt.%, surfactant 0.0015-0.009 wt.%, Hcl 2.0-8.0 wt.%, water - the rest.

Claims (1)

Composition for descaling, consisting of water-soluble sulfur-oxygen-containing compounds, in particular pyrosulphates or sulphurous inorganic salts, characterized in that it additionally contains corrosion inhibitors: polyphenolic compounds of larch and urotropin, as well as surface-active substances (surfactants) in the following components, wt .%: Sodium pyrosulfate or potassium, or ammonium, or sulphate sodium or potassium or ammonium 0.09-10 Polyphenol compounds larch trees 0.003-2 Urotropin 0.01-4 Surfactant 0,0015-0,009 Hcl 2.0-8.0 Water Else