KR100290808B1 - Descaling agent for boiler - Google Patents

Abstract

PURPOSE: A descaling agent incorporating sodium hexametaphosphate, sodium lignosulfonate, sodium hydroxide and polyacrylate copolymer is provided to prevent corrosion and scale deposition on boiler pipe. CONSTITUTION: The descaling agent comprises 0.1-10wt.% of sodium hexametaphosphate, 0.1-5wt.% of sodium lignosulfonate, 2-10wt.% of sodium hydroxide, 1-10wt.% of polyacrylate copolymer represented by chemical formula I, a balance of water. In the chemical formula I, n is an integer of 20 to 100; R1 and R2 are identical or different each other, and denote hydrogen atom, alkyl or hydroxy group. Sodium hexametaphosphate is converted into the form of ortho phosphate in water, and its concentration is maintained between 0.5 and 100ppm. For the optimal performance, each concentration of polyacrylate copolymer, sodium lignosulfonate and sodium hydroxide in circulating water are kept 0.5-50ppm, 0.1-20ppm and 0.5-60ppm, respectively.

Description

Corrosion and scale prevention water treatment composition of boiler and corrosion and scale suppression method of boiler using same

The present invention relates to a water treatment agent composition for preventing corrosion and scale of a boiler and a method for inhibiting corrosion and scale of a boiler using the same, and more specifically, a polyacrylate copolymer, sodium hexametaphosphate, sodium lignosulfonate, and sodium hydroxide. The present invention relates to a water treatment agent composition for corrosion and scale prevention of a boiler effective in preventing corrosion and scale of a low pressure boiler using pure water having completely removed positive and negative ions as a boiler feed water, and a method for inhibiting corrosion and scale of a boiler using the same.

In various industrial facilities where boiler water is needed and in buildings where boiler water is used for heating, the metal surface where the boiler water system is in contact with water, especially the heat transfer surface, may be corroded or generate scale, which may not only be a major obstacle to a smooth circulation system but also thermal efficiency. At the same time as falling, it can even lead to a serious situation in which the canal ruptures.

Recently, newly constructed apartment complexes prefer district heating improved in terms of thermal efficiency in the central heating system, and such district heating is performed at the local cogeneration plant.

Some of the recently built regional cogeneration plants have boilers with a boiler pressure of 40 kgf / cm ² or less and using pure water as feed water. These boilers are more corrosion resistant than scale suppression because the cations and anions that cause scale have been completely removed. Management is more important.

Conventionally, a method of controlling pH using only phosphate and a method of controlling corrosion and corrosion products using phosphate and polymers have been known as a water treatment program to prevent corrosion of low pressure and pure boilers (see US Patent No. 4,931,206). .

Phosphate program of the program is 40kgf / cm ² or more pure water boiler in but has excellent function of inhibiting the overall corrosion of the boiler while suppressing the alkali corrosion, in the pure water boiler is less than 40kgf / cm ² in a state in which the alkali erosion that largely been concerned Since the pH of boiler water is controlled relatively low, it is not effective in inhibiting corrosion, and since the product does not contain dispersant to control hardness scale or metal oxides, when the function of the pretreatment facility or corrosion is caused, There is a disadvantage that the scale component can not be adjusted.

On the other hand, since the phosphate / polymer program is relatively alkaline, the pH is kept high, so it is effective in inhibiting corrosion and the scale control agent is included in the product. However, the use of corrosive materials in steel as a scale inhibitor may result in the corrosion of the scale inhibitor component.

Accordingly, an object of the present invention is to provide a water treatment agent composition for preventing corrosion and scaling of a boiler which exhibits excellent anticorrosive effect and scale prevention in a low pressure, pure boiler water system by completely improving the disadvantages of such conventional water treatment agent compositions.

Another object of the present invention to provide a method for suppressing the corrosion and scale of the boiler by using the water treatment agent composition.

The water treatment agent composition of the present invention for achieving the above object is 0.1 to 30% by weight of a polyacrylate-based copolymer compound represented by the following formula (1), in the composition for preventing corrosion and scale of the boiler, the balance of water Sodium hexametaphosphate 0.1-30 wt%, sodium lignosulfonate 0.1-10 wt% and sodium hydroxide 0.1-30 wt%.

Wherein n is an integer from 20 to 100, and R ₁ and R ₂ are the same as or different from each other, a hydrogen atom, an alkyl group or a hydroxyl group.

In the method of suppressing the present invention for achieving the above another object, in applying the composition to a boiler water system, the polyacrylate copolymer compound represented by the formula (1) when the water treatment program is applied is maintained at 0.5 to 50 ppm, sodium hexa Metaphosphate is broken down into orthophosphate in a boiler to maintain 0.5 to 100 ppm with orthophosphate, sodium lignosulfonate to maintain 0.1 to 20 ppm, and sodium hydroxide to be maintained at 0.5 to 60 ppm. Is done.

Hereinafter, the present invention will be described in more detail.

The water treatment agent composition according to the present invention is 0.1 to 30% by weight, preferably 1 to 10% by weight, sodium hexametaphosphate 0.1 to 30% by weight, preferably 0.1 to 30% by weight of the polyacrylate copolymer compound represented by the following general formula (1) 10% by weight, sodium lignosulfonate 0.1 to 10% by weight, preferably 0.1 to 5% by weight, and 0.1 to 30% by weight sodium hydroxide, preferably 2 to 10% by weight and the balance consists of water.

Formula 1

Wherein n is an integer from 20 to 100, and R ₁ and R ₂ are the same as or different from each other, a hydrogen atom, an alkyl group or a hydroxyl group.

If the amount of the polyacrylate copolymer compound represented by Formula 1 is less than 0.1% by weight, the scale inhibitory effect is insufficient, and if the amount of the polyacrylate copolymer compound is greater than 30% by weight, it may adversely affect corrosion, and the amount of sodium hexametaphosphate If it is less than 0.1% by weight, the pH buffering effect is insufficient, and if it exceeds 30% by weight, the conductivity is increased. In addition, when the amount of sodium lignosulfonate is less than 0.1% by weight, the metal oxide is insufficient in scale control capability, and when it exceeds 10% by weight, turbidity is increased, and when the amount of sodium hydroxide is less than 0.1% by weight, the pH is adjusted. Insufficient capacity, there is a disadvantage in that the conductivity is increased if it exceeds 30% by weight.

When the water treatment agent composition as described above is applied for the internal treatment of the boiler, the pH of the boiler water is preferably applied to 10.5 to 11.5.

Therefore, in applying the water treatment agent composition of the present invention to the boiler water system, the polyacrylate copolymer represented by Chemical Formula 1 is maintained at 0.5 to 50 ppm in the entire boiler water system when the water treatment program is applied, and sodium hexametaphosphate is Ca salt or the like. It is suitable for the treatment of the contained hard water and is decomposed to orthophosphate in the boiler and maintained at 0.5 to 100 ppm with orthophosphate. In addition, sodium lignosulfonate has an excellent effect on the treatment of metal oxides, and it is maintained at 0.1 to 20ppm when the water treatment program is applied, and sodium hydroxide is maintained at 0.5 to 60ppm when the water treatment program is applied to effectively suppress corrosion and scale of the boiler. You can.

On the other hand, if the content of sodium hydroxide in the boiler water is too small, the pH is kept low, so that the corrosion inhibitory effect is insignificant, if too much has an adverse effect of increasing the conductivity. In addition, if the content of polyacrylate, sodium hexametaphosphate and sodium lignosulfonate is too small, the scale inhibitory effect is insignificant, too much is uneconomical, and in the case of polymer may adversely affect corrosion.

As described above, the water treatment agent composition of the present invention has a boiler pressure of 40 kgf / cm ² or less, and is particularly effective in a boiler water system using pure water as boiler feed water.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.

Examples 1-2

The boiler drum pressure was 13 kgf / cm ² and the capacity was 30 tons / hr. The water supply was operated for 30 days using a heating water pipe boiler system using pure water completely free of positive and negative ions.

At this time, to prepare a water treatment composition consisting of the composition shown in Table 2 in the water quality of the feed water as shown in Table 1, added to the water supply line at a rate of 15mg per 1kg of the steam generation amount and the pH of the irrigation water and the concentration of the train are listed in Table 4. .

Item Contents pH 5.7 Conductivity (μS / cm) 2 Calcium hardness (ppm) 0.0 Chlorine Concentration (ppm) 4.0. Iron concentration 0.02 Silica (ppm) 0.5

ingredient Content (% by weight) Example 1 Example 2 water 80.8 82.9 Sodium hydroxide 8 8 Sodium hexametaphosphate 7 6 Polyacrylate 4 3 Sodium League No Sulfonate 0.2 0.1

Comparative Examples 1 to 3

To prepare a water treatment composition consisting of a composition as shown in Table 3, and also tested in the same manner as in Examples 1 to 2 and the pH of the irrigation water at that time and the concentration of the train is shown in Table 4 below.

ingredient Content (% by weight) Comparative Example 1 Comparative Example 2 Comparative Example 3 water 93.15 86.82 79.5 Sodium hydroxide 1.85 0 3.5 Sodium Tripolyphosphate 5 0 6 Sodium hexametaphosphate 0 0 15 Disodium phosphate 0 2.52 0 Trisodium Phosphate 0 10.66 0 Hydroxyethylidenediphosphoric acid 0 0 2.0

division pH Train (ppm) Example 1 11.0-11.5 0.15 or less Example 2 11.0-11.5 0.15 or less Comparative Example 1 9.8-10.2 0.3 or less Comparative Example 2 9.8-10.2 0.3 or less Comparative Example 3 8.2-8.7 0.6 or less

According to Table 4, it can be seen that the results of Examples 1 and 2 according to the present invention for the water quality of Table 1 are relatively lower than the concentration of iron, which is an index of corrosion products in watering, than the results of Comparative Examples 1 to 3. . 40kgf / cm²The following In the low pressure pure water boiler, it can be seen that, as in Examples 1 and 2, it is more effective to suppress corrosion by using a non-corrosive dispersant while keeping the pH as high as possible within the pH control range (10.5 to 11.5).

As described above, the composition of the present invention contains a non-corrosive acrylate copolymer and sodium lignosulfonate, which has a strong dispersibility of hard materials and iron oxides, in particular, excellent pH control ability, less than 40kg of pure water Effective for suppressing corrosion of boilers.

Claims (3)

In the composition for preventing corrosion and scale of boilers, 0.1 to 30% by weight of polyacrylate-based copolymer compound represented by the following formula (1), sodium hexametaphosphate, 0.1 to 30% by weight, and sodium league, based on the total composition of water balance A water treatment agent composition for preventing corrosion and scaling of a boiler, characterized in that consisting of 0.1 to 10% by weight of nosulfonate and 0.1 to 30% by weight of sodium hydroxide. Formula 1

Wherein n is an integer from 20 to 100, and R ₁ and R ₂ are the same as or different from each other, a hydrogen atom, an alkyl group or a hydroxyl group. The method according to claim 1, wherein the polyacrylate copolymer compound is 1 to 10% by weight, sodium hexametaphosphate is 0.1 to 10% by weight, sodium lignosulfonate is 0.1 to 5% by weight, sodium hydroxide is Water treatment agent composition for preventing corrosion and scale of the boiler, characterized in that 2 to 10% by weight. In applying the composition according to claim 1 in the boiler water system, the polyacrylate copolymer compound represented by the following formula (1) when the water treatment program is applied is maintained at 0.5 to 50ppm, sodium hexametaphosphate is orthophosphate in the boiler Decomposed to orthophosphate and maintained at 0.5 to 100 ppm, sodium lignosulfonate is maintained at 0.1 to 20 ppm, sodium hydroxide is added to be maintained at 0.5 to 60 ppm corrosion of the boiler of the boiler and Scale suppression method. Formula 1

Wherein n is an integer from 20 to 100, and R ₁ and R ₂ are the same as or different from each other, a hydrogen atom, an alkyl group or a hydroxyl group.