CS249530B2 - Agent on base of organic acids for removal of mineral deposits especially of boiler incrustation - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a means for removing mineral deposits and, in particular, scale, formed in cooling circuits and in systems where water or steam flows. Chemical descaling is based on dissolving the sediment with solutions of suitable agents and is generally known.

Chemical methods for removing unwanted deposits are used more often than mechanical methods that are labor intensive, difficult, and can cause mechanical damage to the equipment to be cleaned. Moreover, dry cleaning is definitely more efficient and is often the only possible way of removing unwanted deposits, for example in the case of coil tubes, heat exchanger tubes and condenser tubes.

Mineral deposit removal chemicals usually contain an organic or inorganic acid as active ingredient and a mixture of organic and inorganic compounds as a corrosion inhibitor. The choice of the active ingredient and the corrosion inhibitor depends, for example, on the type of metal to be treated, on the type and amount of mineral deposit and on the operating conditions of the device.

From Polish Patent Nos. 68,703 and 117,201, chemical agents for scaling are known, in particular from cast iron surfaces: they are aqueous solutions of hydrochloric acid and nitric acid with the addition of a corrosion inhibitor, for example hexamethyloltetramine and phosphoric acid (U.S. Pat. 68,703) and sodium formate, sodium dihydrogen phosphate and potassium dichromate (U.S. Pat. No. 117,201). Polish patent No. 105 961 discloses a means for removing scale from units of various construction materials, for example steel, copper or brass, based on citric acid, containing as a corrosion inhibitor, for example benzotriazole, stannous chloride and optionally benzylsulfoxide or amine.

USSR 378 571 discloses a scaling agent from a device where steam or water based on citric acid is flowing, containing benzotriazole, hydrazine hydrate and a disodium salt of ethylenediaminetetraacetic acid as a corrosion inhibitor.

In U.S. Pat. No. 4,279,768 discloses ^one means for removing mineral deposits from the heat exchanger, containing complexing agents, such as tetrasodium EDTA and tetrasodium nitrotrioctové acid alone or in admixture, benzotriazole, and sodium sulphate and natriumglukonát.

From German Patent Specification No. 900 030 there is known a composition for. scaling, which contains a 15% solution of amidosulfonic acid with the addition of organic sulfides as corrosion inhibitors.

It is an object of the present invention to provide a device for cleaning devices of different metals or different metal alloys, which has a high efficiency in removing mineral deposits of different chemical compositions.

Surprisingly, it has now been found that this objective can be achieved by maintaining a suitable ratio of acetic acid, alicyclic amine acetate and metal acetate of the fourth period of the Mendeleyev system of elements.

Accordingly, the present invention relates to an organic acid composition for removing mineral deposits and, in particular, scale, formed in cooling circuits and water or steam-operated plants, characterized in that it contains 0.3 to 30% by weight of acid acetic, 0.01 to 5% of at least one alicyclic amine acetate with one or two rings of 6 carbon atoms, 0.1 to 10% of at least one acetate of copper, zinc, iron, molybdenum, manganese, nickel or cobalt; 100% water.

The cleaning according to the invention is carried out at a temperature of 280 to 330 K. The cleaning time depends on the amount and composition of the sediment and on the temperature of the cleaning solution used, and is several hours to several tens of hours.

The advantage of the composition according to the invention is its easy manufacture, protecting the action on metals, flame retardancy and explosion-proofness. Another advantage is the possibility of reuse. After the purification process, the solution used can be reused for further purification after the addition of the corresponding active ingredients. This allows considerable savings in both active substance and water and also reduces the amount of waste water.

Tests carried out on the removal of mineral deposits by the composition of the invention from the heat exchanger and other energy devices of various metallic materials have demonstrated the high efficiency and usefulness of the composition of the invention. The device according to the invention even made it possible for a device which had already been put out of use for complete clogging of deposits.

The following practical examples do not limit the invention. Percentages are meant by weight only.

Example 1

A medium containing 2 percent acetic acid, 0.2% dicyclohexylamine acetate, 0.2% copper acetate, 0.2% zinc acetate, 0.85% acetate was introduced into the carbon steel rotor and brass MC-70 heat exchanger in the circulation system. ferrous and 97.35% water. The cleaning was carried out at 290-295 K. (After 30 hours of circulation, the outlet pressure was reduced from 0.36 MPa to 0.14 MPa, at this value stabilized, confirming complete removal of the deposit.

Example 2

Into oxygen-free cooling tubes of 0 6 X 1 mm, soldered to the diffusion pump frame at an inlet pressure of 0.3 MPa and a flow rate of 0.2 dm ³ / min. A composition comprising 2% acetic acid, 0.5% methylcyclohexylamine acetate, 0.3% copper acetate and 97.2% water is introduced into the circulation. The cleaning is carried out at a temperature of 290 to 295 K. After 18 hours of circulation of the composition, the flow rate is unchanged at 2.1 dm ³ per minute; the fact that this flow rate is steady indicates the removal of scale.

Example 3

To a steel steam generator (St 3S) with a thermal efficiency of 2.45 X 10 ⁵ kj / h, at a pressure of 4 MPa, an initial flow rate of 8 l / min. at 0.4 MPa at the point of entry into circulation, a composition consisting of 12.0% acetic acid, 0.1% cyclohexylamine acetate, 0.02% dicyclohexylamine acetate, 0.3% iron (III), zinc and manganese acetate and 87% is introduced; 5% water. After 4 hours of circulation at unchanged inlet pressure, the flow rate is 35 liters / h and does not change over time, indicating complete scaling.

Example 4

The turbine capacitor was initially treated for 2 days with an etching mixture of 5 to 7% hydrochloric acid, 0.5% urotroin. After cleaning, 430 brass pipes were found to have perforations. In addition, 30% of the original deposits in the tubes remained. After two years of operation, the unit was cleaned again, this time for three days with the composition of the invention: 6% acetic acid, 0.1% cyclohexylamine acetate and dicyclohexylamine acetate, 0.05% copper acetate, 0.05% zinc acetate and the rest water . After cleaning, no new perforations were detected, with 5% of the tubes showing a slight residue and 95% of the tubes having a clean surface.

Example 5

A comparative corrosion test was performed to remove mineral deposits with an aqueous acetic acid solution without a corrosion inhibitor and a composition according to the invention.

A mineral precipitate of 80.5% calcium carbonate, 2.67% magnesium oxide, 1.44% silica, 8.5% ferric and ferrous 2% acetic acid was dissolved; the mineral precipitate insoluble in hydrochloric acid was 6.8%. Carbon steel was etched during this removal of mineral deposits; etching is 43 g / m ² , 24 h.

When using a composition according to the invention of 2% acetic acid, 0.2% cyclohexylamine acetate, 0.05% zinc acetate, the dissolution rate of carbon steel is 5.3 g / m ² , 24 h, with the dissolution rate of the above mineral deposit three times greater than using acetic acid alone.

Examples 6 to 28

Examples 6 to 28 are in the following table.

Table

Removal of mineral deposits, particularly scale, of 50 to 85% calcium carbonate, 0.5 to 6% magnesium oxide, 0.9 to 18% ferrous iron oxide, 0 to 2.0% copper oxide, 0.2 to 3% oxide silica, 0 to 3% phosphorus pentoxide-calcium sulphate, 1% zinc + copper + alumina and other components of test tube shaped bodies for various heat exchangers by means of the invention

Sample СНзСООН Aminoacetates Metal acetates

number % CHA DCHA % methylCHA Fe Zn Cu 1 0.3 0.01 - - 0.1 0.1 - 2 1.0 0.01 0.01 0.02 0.5 - 3 3.0 0.01 0.01 0.02 0.5 - - 4 5.0 0.05 0.01 0.03 1.0 0.5 - 5 5.0 1.00 2.00 2.00 5.0 1.0 - 8 5.0 1.00 1.00 1.00 - 3.0 2,0 7 5.0 0.50 0.30 0.20 2,0 - - 8 8.0 0.05 0.15 5.8 - - 9 8.0 0.05 0.3 0.15 5.8 - - 10 8.0 0.5 - - 4.2 - - 11 8.0 0.5 0.1 0.2 1.0 1.0 2,0 12 10.0 0.06 - 0.2 2,0 - - 13 10.0 - 0.1 0.2 2,0 - - 14 10.0 - 0.3 0.5 4.8 1.0 - 15 Dec 10.0 - - 1.0 4.8 1.0 - 16 15.0 1.0 1.0 1.0 0.3 0.1 - 17 15.0 1.0 1.0 1.0 - 0.5 0.5 18 15.0 1.0 0.5 0.1 4.8 1.0 - 19 Dec 15.0 1.0 0.5 0.1 4.8 1.0 - 20 May 20.0 0.5 0.5 0.5 5.8 - 21 20.0 0.5 0.5 0.5 - 5.0 1.0 22nd 20.0 0.5 0.5 0.5 4.8 1.0 25 20.0 0.5 0.05 0.1 4.8 1.0 - 27 Mar: 27.0 1.0 1.0 1.0 6.3 0.7 - 28 27.0 1.0 1.0 1.0 6.3 0.7 -

Mn Metal acetates Mo What Temperature ° C AND g / 24 h In g / m ² .24 h C _ _ _ 22nd 1.3 10.1 carbon steel 0.1 - - 22nd 5.2 8.3 carbon steel 0.1 - - 22nd 6.1 7.8 carbon steel - - 22nd 9.8 5.3 carbon steel 0.5 - - 22nd 16.3 2.3 carbon steel - 0.1 0.2 22nd 12.8 0.14 brass 1.0 1.0 1.0 22nd 13.5 0.09 austenitic steel 1,2 0.3 0.2 22nd 17.3 1,8 carbon steel 1,2 0.3 0.2 55 25.8 1.9 carbon steel 0.5 0.1 0.1 22nd 14.3 8.3 carbon steel - 0.1 55 22.8 0.3 brass 0.6 0.4 0.1 55 18.9 0.3 austenitic steel 0.6 0.4 0.1 22nd 23.4 0.09 austenitic steel 0.1 0.3 22nd 19.3 4,5 carbon steel 0.1 0.3 - 22nd 17.1 5.4 carbon steel 0.1 - - 22nd 14.7 8.3 carbon steel - - 22nd 13.8 1,2 brass 0.5 0.5 - 22nd 15.7 6.3 carbon steel 0.5 0.5 - 22nd 16.1 0.3 austenitic steel 1.0 - - 22nd 19.3 4.6 carbon steel - - 22nd 18.7 1.3 brass 0.5 0.5 0.3 22nd 18.5 0.6 austenitic steel 0.5 0.3 0.7 55 13.1 0.9 austenitic steel - - 22nd 11.3 7.3 carbon steel - - - 55 18.3 9.7 carbon steel

А · = solubility of precipitate В = solubility of metal C = pipe material

R-35 carbon steel tubes are 32 and 57 mm in diameter, 70, 10 and 24 mm brass, and 1H18N9T 34 mm steel. Measurement of material solubility is performed on the same tubes after mechanical processing (production and grinding) by weighing.

Claims (1)

An organic acid-based composition for removing mineral deposits and, in particular, scale, formed in cooling circuits and water or steam installations, characterized in that it contains from 0.3 to 30% by weight of acetic acid, from 0.01 to 30% by weight. 5% of at least one alicyclic amine acetate with one or two rings each having 6 carbon atoms, 0.1 to 10% of at least one acetate of copper, zinc, iron, molybdenum, manganese, nickel or cobalt and up to 100% water.