RU2339586C1 - Method of scale removal and protection against salt deposit and corrosion - Google Patents

Abstract

FIELD: chemistry, technological processes.

SUBSTANCE: method includes introduction into system of heat exchangers of washing composition, containing pyrosulfates or inorganic oversulfites, hydrolisable alkaline salts of larch bark tannin, anion-active surface-active substances (SAS), as well as acid and water with the following content of components (wt %): sodium, potassium, ammonium pyrosulfate or sodium, potassium or ammonium oversulfite - 0.9-10; hydrolisable alkaline salts of larch bark tannin 0.5-6; anion-active SAS 0.0015-0.009; HCl - 2.0-8.0; water - remaining part. After carrying out purification with washing composition, inhibiting scale formation and corrosion composition is introduced into heat-exchangers system, which contains following components in ratio (wt %): hydrolisable alkaline salts of larch bark tannin 0.5-2; anion-active SAS 0.0015-0.009; water - remaining part.

EFFECT: low corrosion rate at washing stage, enhancing protective properties of compositions, extension of range of ecologically safe and less expensive inhibiting means.

3 cl, 1 tbl, 6 ex

Description

The invention relates to the petrochemical, chemical industry, power engineering, water supply and other sectors of the national economy, and in particular to compositions for descaling the surface of pipes, heat exchangers, process apparatuses and protecting equipment from salt deposition and corrosion.

Thus, the operation of heat exchangers under increased loads, such as for example diesel locomotives in high altitude conditions, is accompanied by a high salt deposition rate and corrosion. This leads to significant power losses, frequent stops for equipment repair, the need for their regeneration to restore heat transfer and, as a result, to large economic losses.

This requires the introduction of washing liquid to remove scale, corrosion inhibitors and film-forming inhibitors. As inhibitors, both individual inorganic and organic compounds, for example, phosphates, chromates, molybdates, tungstates, nitrites, other salts of inorganic acids, alkyl or aryl carboxylates, amino acids, sulfonates and alkyl phosphates, as well as compositions of several substances (Chemical Encyclopedia, vol. 2. - M.: Soviet Encyclopedia, 1990. - 222 p., Margulova T.Kh. Use of complexones in the power system. - M .: Energoatomizdat, 1986, p. 253). Inorganic inhibitors effectively inhibit corrosion in neutral environments, but are toxic and expensive reagents. In addition, in the presence of chlorine ions, they can provoke pitting (local or pitting) corrosion. Hydrochloric corrosion proceeds quite intensively due to the residual concentration of chloride ions that are most often used in washing solutions. In view of this, even with deep washing, the supply of significant quantities of inhibitors is required (F.I. Skalozub, D.N. Levchenko // Oil refining and petrochemicals: NTIS. - M .: TsNIITEneftekhim, 1982. - No. 9. - p.6-7) .

A known method of descaling using a composition that includes (wt.%) Bischofite 39.3-52.0; acetic acid 1.0-3.0; water - the rest (Application RU No. 94013163).

The disadvantage of this method is the low activity of the composition used in the removal of scale and a sufficiently high corrosion activity.

Also known is a method of descaling using 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.

With a sufficiently high activity in descaling, the disadvantage of this composition is its high corrosion activity to the metal surfaces of the equipment due to the absence of corrosion inhibitors in the composition.

The closest in technical essence and the achieved effect to the proposed invention is a washing method using a composition (Patent RU No. 2257354) containing sodium pyrosulfate, or potassium, or ammonium, or sodium sulphate, or potassium, or ammonium 0.09-10.0 , hydrochloric acid 2.0-15.0, urotropin 0.01-4.0, nonionic surfactant 0.0015-0.009, polyphenolic compounds of coniferous bark 0.003-2.0, polyhexamethylene guanidine chloride 0.1-1.5, water - the rest.

The proposed method is characterized by a sufficiently high activity of the used composition for descaling, however, the disadvantages of this method are the high cost of polyhexamethylene guanidine used as inhibitors of polyphenols and chloride, their high toxicity. Also, the equipment’s protection against salt deposition and corrosion during the long-term operation of the equipment when using urotropin is not high enough. As shown by the practice of using an aqueous solution of urotropin to neutralize hydrogen chloride, a characteristic of urotropin is its high ability to form deposits in heat exchange equipment and low anticorrosive efficiency (Patent No. RU 2221837). The corrosion rate determined in laboratory conditions when using an aqueous solution of urotropine as a neutralizer was 0.015 mm / year. In this case, pitting corrosion was mainly manifested.

The objective of the invention is the creation of a more efficient, cheap, environmentally friendly method of descaling and protection against salt deposits and corrosion.

The task is achieved by the fact that the washing system containing pyrosulphates or sulphurous inorganic salts, hydrolyzable alkaline salts of larch bark, anionic surfactants, as well as acid and water at the following content of components (wt. .%):

sodium, potassium, ammonium pyrosulfate or sodium, potassium or ammonium sulphate 0.9-10 hydrolyzable alkaline salts of tannin bark of larch 0.5-6 anionic surfactants 0.0015-0.009 Hcl 2.0-8.0 Water rest,

and after descaling with the above flushing composition, a scale inhibiting and corrosion inhibiting composition containing the following components in the ratio (wt.%) is introduced into the heat exchanger system:

hydrolyzable alkaline salts of tannin bark of larch 0.05-0.2 anionic surfactants 0.0015-0.009 water rest.

The initial (shock) dose of the inhibitory composition depends on the total hardness of the make-up water and is 0.05 (wt.%), With a water hardness of less than 2 mEq / dm ³ , with a hardness of make-up water of more than 2 mEq / dm ³ the initial consumption of hydrolyzable alkaline salts of larch bark tannin in the composition is 0.2 (wt.%), and to maintain the inhibitory effect of the solution in the future, the required consumption of hydrolyzable alkaline salts of larch bark tannin in the composition is at least 0.05 (wt.%).

Anionic surfactants are used as surfactants.

Extracts of hydrolyzed alkaline salts of tannin are extracts from the bark of larch Daurian, Siberian (Larix sibirica Ledeb and Larix dahurica Turch. A synonym for L. gmelinii (Rupr.) Rupr.), Plant waste obtained at the stage of debarking of larch wood in the process of obtaining cellulose from it treatment with a 0.1-1 N solution of sodium hydroxide at a temperature of 60-90 ° C for 0.5 h at a mass ratio of T: W equal to 1: 5-6, followed by separation of the resulting solution and concentration.

The method is as follows.

The washing of the cooling systems is carried out by circulation of the washing composition containing (wt.%):

sodium, potassium, ammonium pyrosulfate or sodium, potassium or ammonium sulphate 0.9-10 hydrolyzable alkaline salts of tannin bark of larch 0.5-6 anionic surfactants 0.0015-0.009 Hcl 2.0-8.0 Water rest,

in the system when the equipment is in normal operation for at least 72 hours.

In this case, the scale loosens and falls into the solution in the form of sludge, which is removed from the system by blowing it with water. The surface is cleaned of scale, including all inaccessible places, while due to diffusion a protective film is formed on the surface, which protects the surface from re-scale formation. This is because organic inhibitors are adsorbed only on the surface of the metal. The corrosion product does not adsorb them. Conclusion of salt corrosion products and mechanical impurities from water circulating systems is carried out using mechanical filters.

After cleaning with a flushing composition, an inhibiting scale and corrosion inhibiting composition is introduced into the heat exchanger system, containing the following components in a ratio (wt.%):

hydrolyzable alkaline salts of tannin bark of larch 0.05-0.2 anionic surfactants 0.0015-0.009 water rest,

moreover, the initial (shock) dose of the inhibitory composition depends on the total hardness of the make-up water and is 0.05 (wt.%), with a water hardness of less than 2 mEq / dm ³ , with a hardness of make-up water of more than 2 mEq / dm ³ the consumption of hydrolyzed alkaline salts of larch bark tannin in the composition is 0.2 (wt.%), and to maintain the inhibitory effect of the solution in the future, the required consumption of hydrolyzed alkaline salts of larch bark tannin is at least 0.05 (wt.%).

A distinctive feature of the invention is that in the present invention, hydrolyzable alkaline salts of larch tannin (Larix sibirica Ledeb and Larix dahurica Turch. Synonym for L. gmelinii (Rupr.) Rupr.) Are used as inhibitors, and anionic surfactants are used as surfactants.

Under operating conditions of the equipment, the alkaline salts of tannin are capable of reversibly hydrolyzing, forming complexes of calcium and magnesium salts in the solution, and they are active sludge-forming agents removed from the cooling system. Thus, the introduction of hydrolyzable alkaline salts of tannins into the composition of the washing solution promotes the release of salts involved in scale formation in the solid phase as a result of physical and chemical processes. In this case, the inner surface of the heating or heat transfer is cleaned of scale to a technically pure state, including all inaccessible places.

In the process of corrosion, a change in the composition of the medium occurs and a protective coating film is formed on the correlating surface on the heating or heat transfer surfaces, which protects the surface from re-scale formation. In the first hours of testing, a loose, fragile film of corrosion products forms on the surface of the steel. With an increase in the exposure time, depending on the concentration of the inhibitor, the film is rearranged: a loose precipitate disappears, a dense, shiny dark gray (sometimes almost black) film grows on the surface - a screening surface that sharply reduces the corrosion rate (up to 13 times), increasing the degree of metal protection up to 92%.

In the environment to be cleaned, conditions are created under which scale-builders in the system with multiple circulation that accumulate when replenished with water are released only in the form of sludge, unable to stick to the walls of pipes covered with a protective film, and removed from the system into the sludge collector.

As a source of plant materials subjected to alkaline extraction, waste is obtained from the debarking of Daurian and Siberian larch (Larix sibirica Ledeb and Larix dahurica Turch. Synonym for L. gmelinii (Rupr.) Rupr.)

In the reactor, larch bark is extracted by heating the feed in aqueous alkali solutions in a water bath (without boiling) for 0.5 hours. The data obtained by us showed that the condensation process is controllable and proceeds in time. An increase in extraction time leads to an increase in the share of non-hydrolyzable tannins (N.V. Goncharova, M.V. Tok, T.V. Ryazanova. Chemistry of plant raw materials 2 (1998) N2, pp. 75-78). The aqueous extract is an extract obtained at a mass ratio of solid: liquid, equal to 1 / 5-6, followed by separation of the resulting solution and its concentration, for example, by evaporation on a rotary evaporator 5-6 times. The density of the resulting aqueous extract is 0.99-1.2 g / l, the concentration is 15-20%. The alkaline salts of larch tannin (Larix sibirica Ledeb and Larix dahurica Turch. Synonym for L. gmelinii (Rupr.) Rupr.), Isolated under the above conditions, are capable of reversible hydrolysis.

Comparative analysis with the prototype shows that this method of descaling and protecting equipment from corrosion using tannin as a corrosion inhibitor in the compositions of hydrolyzed alkaline salts meets the novelty criterion. The use in this composition of hydrolyzable alkaline salts of tannin in combination with known components at their indicated ratio provides properties that are manifested only in this technical solution: high corrosion stability of the compositions relative to the cooling system. When studying other technical solutions in this field of technology, signs that distinguish the claimed invention from the prototype were not identified, which ensures that this technical solution meets the criterion of significant differences.

The effectiveness of the proposed method of corrosion protection using larch tannin as inhibitors of hydrolyzable alkaline salts was tested on samples of low-carbon steel St3 in a solution of a scale converter. The prototype solution was used as a reference (Patent RU No. 2257354, Example No. 6). Under similar conditions, the compositions shown in the remaining examples were analyzed.

Tests for the corrosion activity of the proposed compositions in scale converters were carried out in a stationary mode according to the method (P.A. Akolzin. Control of metal corrosion of boilers. - M .: Energoatomizdat, 1994, p. 115). Before testing, the metal samples were thoroughly cleaned, polished, etched in a 10% sulfuric acid solution with the addition of thiocarbamide, degreased with acetone and weighed. Prepared fat-free and dried at a temperature of 110 ° C, cooled to room temperature, 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 with complete immersion of the samples.

The corrosion rate was determined according to GOST 9.908-85 by the gravimetric method using analytical scales VLR-200 and calculated by the formula:

where Δm is the change in mass, g; S is the sample area, m ² , t is the duration of the experiment, h

The degree of inhibition of deposits or the degree of corrosion protection Z (in%) was determined by the formula:

Z = K ₀ -K ₁ / K ₀ × 100%

where K ₀ and K ₁ [g / (m ² · h)] is the dissolution rate of the metal in the medium without the introduced inhibitor and with the inhibitor, respectively. With full protection, the Z factor is 100%.

After testing, the samples were removed from the solution, corrosion products were carefully removed, dried, cooled and weighed again. The 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, during 72 hours of testing tap water was evaporated 4 times. The initial salt content of 0.150-0.200 g / l, the content of Ca ^{2+ ions} 25-40 mg / l. The samples were plates from St. 10 (74 × 20 × 4.7 mm), sanded and degreased with toluene and ethanol. The plates were placed in the test solution and kept in it at a temperature of 40-42 ° C for 30 days with continuous purging with air. The corrosion rate was calculated by the loss of weight of the plate after the experiment and was counted in mm / year. In the absence of an inhibitor, the corrosion rate was 0.41 mm / year.

Example No. 1. In a composition containing (wt.%): Sodium pyrosulfate - 0.1; hydrolyzed alkaline salts of tannin bark of larch - 12; anionic surfactants - 0.0015; HCl - 8.0; water is the rest.

Example No. 2. In contrast to example 1, the composition with the content (wt.%): Ammonium pyrosulfate - 10; hydrolyzed alkaline salts of larch bark tannin - 6; anionic surfactants - 0.0015; HCl - 8.0; water is the rest.

Example No. 3. In contrast to example 1, the composition with the content (wt.%): Potassium sulphate - 10; hydrolyzed alkaline salts of larch bark tannin - 1.0; anionic surfactants - 0.009; HCl - 8; water is the rest.

Example No. 4. In contrast to example 1, the composition with the content (wt.%): Ammonium pyrosulfate - 10; hydrolyzed alkaline salts of larch bark tannin - 0.25; anionic surfactants - 0.0015; HCl - 2; water is the rest.

Example No. 5. In contrast to example 1, the composition with the content (wt.%): Ammonium pyrosulfate - 11; hydrolyzed alkaline salts of larch bark tannin - 10; anionic surfactants - 0.009; HCl - 4; water is the rest.

Example No. 6. The composition presented in the prototype with a content (wt.%): Sodium pyrosulfate, or potassium, or ammonium, or sodium sulphate, or potassium, or ammonium - 10.0, hydrochloric acid - 7.5, urotropin - 2.0, polyphenol coniferous bark compounds - 1.0, polyhexamethylene guanidine chloride - 0.75, nonionic surfactant - 0.0015, water - the rest.

The results of corrosion tests of the above examples are presented in table No. 1.

Table 1
The dissolution rate of scale and the degree of corrosion protection for examples 1-6 Example No. The dissolution rate of scale relative to the composition shown in example 6,% The degree of corrosion protection relative to the composition shown in example 6,% Nature of corrosion one 124 79 uniform 2 161 53 uneven 3 89 61 uniform four 81 54 uneven 5 34 82 uniform 6 one hundred 0 pitting

As can be seen from the data presented in table 1, an increase in the content of hydrolyzable alkaline salts of tannin bark of larch slows the rate of dissolution of scale (example No. 5). The decrease in their content increases corrosion (examples No. 2 and 3). In the absence of hydrolyzable alkaline salts of larch bark tannin (example No. 6), the highest value of corrosion is observed, and most importantly, pitting corrosion is the formation of corrosive ulcer cavities (pitting) in the metal. The formation of pitting (example No. 6) can be explained by the low concentration of polyphenols, the action of which, as weak acids, is partially neutralized by polyhexamethylene guanidine chloride, and the resulting protective layer is not strong enough. This fact is explained by the fact that there are active sites on the metal surface and oxygen adsorption at these sites (“ledges”) dramatically reduces the rate of metal dissolution. Adsorbed oxygen molecules, as it were, “lock” the ledges, thereby blocking the ionization process in these most active places.

In the range of pH values from 4 to 10, the surface of the iron is in contact with an alkaline solution saturated with hydrated hydroxide of iron (II), the pH of which is 9.5. The use of a solution of hydrolyzable alkaline salts of tannin bark of larch shifts the passivation potential towards more negative values, i.e. facilitates the transition of the metal to a passive state.

Also, the use of a nonionic surfactant does not contribute to a decrease in the corrosion rate, since the use of anionic surfactants as a release component simultaneously enhances the effect of anodic inhibitors or passivators.

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 No. 4) reduces the rate of dissolution of scale, which increases the surface treatment time.

The most optimal are given in examples No. 1, 2, 3 and 4 of the concentration of the ingredients of the composition: sodium, potassium, ammonium pyrosulfate or sodium sulphate, potassium or ammonium - 0.9-10 (wt.%), Hydrolyzed alkaline salts of larch bark tannin 0 5-6 (wt.%), Anionic surfactants 0.0015-0.009 (wt.%), HCl - 2.0-8.0 (wt.%), Water - the rest.

Industrial tests of the inhibitory composition for protection against scale and corrosion were carried out on the cooling system of locomotives of the 3TE10M type.

Example 7. The composition was used in accordance with the claimed in patent RU No. 2257354 (prototype). Launch diesel locomotive. The first 72 hours the diesel engine operates in a "gentle" mode. After washing the cooling system of the diesel engine, the water is drained and the cooling system is washed with clean water at a pressure of 4-5 atm until water is formed in the outlet with a transparency equal to the inlet water.

In the period from 7 to 21 days of operation in high altitude conditions, the thickness of the formed scale on the surface of the heat exchanger and the state of the coolant and heat transfer were analyzed. When examining the surface of diesel heat exchangers, the following results were obtained:

1. The surface of the heat exchangers did not contain any traces of scale.

2. The coolant is clear, dark brown.

3. Heat transfer amounted to 95-97%.

After running diesel locomotives for 90-180 days, the following results were obtained:

1. A dense dark brown precipitate forms on the surface of the heat exchangers. The layer thickness after operation for 90 days was 0.3-0.6 mm. The layer thickness after operation for 180 days was 1.7-2.3 mm. Pitting was observed on the metal surface.

2. The coolant is clear.

3. Heat transfer amounted to 72-75%.

Example 8. The tests were carried out under the conditions of example 7 on the cooling system of locomotives type 3TE10M.

After washing the locomotive under the conditions of example 7 with a composition containing the following components in the ratio (wt.%): Sodium, potassium, ammonium pyrosulfate or sodium sulphate, potassium or ammonium 0.9-10, hydrolyzable alkaline salts of larch bark tannin 0.5-6 , anionic surfactants 0.0015-0.009, HCl 2.0-8.0, water - the rest, hydrolyzed alkaline salts of tannin bark of larch in a concentration of 0.05-0.2 (wt.%) make-up water are added to the cooling system. The initial (shock) dose of hydrolyzed alkaline salts of tannin bark of larch depends on the total hardness of the make-up water and is 0.05 (wt.%) When the water hardness is less than 2 mEq / dm ³ . When the hardness of the make-up water is more than 2 mEq / dm ^{3, the} initial consumption of hydrolyzable alkaline salts of larch bark tannin is 0.2 (wt.%). Subsequently, an inhibitory scale and corrosion composition is introduced into the heat exchanger system, containing the following components in a ratio (wt.%):

hydrolyzable alkaline salts of tannin bark of larch 0.05-0.2 anionic surfactants 0.0015-0.009 water rest.

In the period from 7 to 21 days of operation in high altitude conditions, the following results were obtained:

1. The surface of the heat exchangers did not contain any traces of scale.

2. The coolant is clear, dark brown.

3. Heat transfer amounted to 95-97%.

After running diesel locomotives for 90-180 days, the following results were obtained.

1. A dense dark brown precipitate forms on the surface of the heat exchangers. The layer thickness after operation for 90 days was 0.1-0.3 mm. The layer thickness after operation for 180 days was 0.4-0.7 mm. Uniform corrosion was observed on the surface of the heat exchanger.

2. The coolant is clear. The sump contains dark brown flakes.

3. Heat transfer amounted to 87-92%.

As can be seen from the above examples 7 and 8, the use of larch bark tannin and anionic surfactants in the inhibiting composition of hydrolyzed alkaline salts of tannin bark reduces the dissolution rate of metallic iron and slows down or prevents the formation of pits. The operation of diesel locomotives with additives to the heat exchangers of hydrolyzed salts of larch tannin showed that this composition of inhibitors can be attributed to passivators. These inhibitors cause the formation of a protective film on the metal surface and contribute to the transition of the metal to a passive state. Crystallization does not occur on pipe walls and heating surfaces, but in the bulk of the solution, while bridging bonds between the surfaces of the particles are formed, linking individual particles into large agglomerates. Deposits of calcium, magnesium salts, as well as sulfate, silicate, silty, glandular deposits form stable suspended flakes with tannin salts. The developed surface of the flakes adsorbs microparticles and organic substances. In this case, there is a shift in the surface potential of the metal of the heat exchangers in a positive direction. This leads to the occurrence of complexation processes in the solution, coagulation of particles, and precipitation in the sludge collector over time, which provides a reliable mechanism for the interaction of the anticorrosive composition with the treated surface, including due to the occurrence of chemisorption processes. In this case, the active centers formed on the metal surface are blocked and a uniform oxide layer is formed. If the oxide has a dense structure, the metal is passivated and corrosion slows down.

The most widely used passivating inhibitors are used to combat corrosion in neutral or similar environments where corrosion occurs predominantly with oxygen depolarization. Such passivators are characterized by critical concentrations. The best protection effect is achieved when the passivator concentration in the solution is exceeded above its critical value. At concentrations below this value, passivators act as cathodic depolarizers and sharply increase the rate of metal corrosion in the active state.

Therefore, the optimal concentration of hydrolyzable salts of tannin larch, shown in example 8.

The technical result of the invention is:

- ensuring a low corrosion rate at the washing stage;

- increasing the protective properties of compositions exhibiting higher anti-corrosion properties due to passivation of the equipment surface;

- expanding the range of environmentally friendly and less expensive inhibitory agents.

Claims (3)

1. A method of descaling and protection from salt deposits and corrosion, including introducing into the heat exchanger system a flushing composition containing pyrosulphates or sulphurous inorganic salts, surfactants, and also acid and water, characterized in that the flushing composition is introduced, containing pyrosulphates or sulphurous inorganic salts, hydrolyzable alkaline salts of tannin bark of larch, anionic surfactants, as well as acid and water at the following content of components entov, wt.%: sodium, potassium, ammonium pyrosulfate or sodium, potassium or ammonium sulphate 0.9-10 hydrolyzable alkaline salts of tannin bark of larch 0.5-6 anionic surfactants 0.0015-0.009 Hcl 2.0-8.0 water rest and after cleaning with a flushing composition, an inhibiting scale and corrosion inhibiting composition is introduced into the heat exchanger system, containing the following components in a ratio, wt.%: hydrolyzable alkaline salts of tannin bark of larch 0.05-0.2 anionic surfactants 0.0015-0.009 water rest 2. The method according to claim 1, characterized in that the initial (shock) dose of the inhibitory composition depends on the total hardness of the make-up water and is 0.05 wt.% With a water hardness of less than 2 mEq / dm ³ , with a hardness of make-up water more 2 mEq / dm ^{3 the} initial consumption of hydrolyzable alkaline salts of larch bark tannin in the composition is 0.2 wt.%, And to maintain the inhibitory effect of the solution in the future, the required flow rate of hydrolyzable alkaline salts of larch bark tannin is at least 0.05 wt.% . 3. The method according to claim 1, characterized in that the hydrolyzable alkaline extracts are an extract from the bark of larch Daurian, Siberian (Larix sibirica Ledeb and Larix dahurica Turch. A synonym for L. gmelmii (Rupr.) Rupr.), Plant waste obtained on stage debarking of larch wood in the process of obtaining cellulose from it by treatment with 0.1-1 N sodium hydroxide solution at a temperature of 60-90 ° C for 0.5 h at a mass ratio of T: W equal to 1: 5-6, followed by separation the resulting solution and concentration.