JP3958706B2 - Water treatment agent - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of water treatment related to iron-based corrosion prevention and scale adhesion prevention in cooling and heating water systems and boiler water systems.
[0002]
[Prior art]
Conventionally, in cooling and heating water systems and boiler water systems, corrosion and scale failures have occurred in piping and heat transfer surfaces such as iron in contact with water.
In cooling and heating water systems and boiler water systems, circulating water that comes into contact with the atmosphere is operated in a highly concentrated state for the purpose of resource conservation, so dissolved salts are also concentrated, causing corrosion, and in piping and heat transfer surfaces. A slightly soluble salt was deposited as a scale.
[0003]
As for corrosion in pipes, chloride ions and sulfate ions, which are called corrosive ions, are not removed in generally used soft water, so these substances are concentrated in boiler water and cause corrosion. The obstacle which corrodes the iron of a boiler can with the dissolved oxygen which is a substance has occurred. In order to remove these obstacles, “deoxygenation method”, “anticorrosion film formation method”, “potential method”, etc. are generally known. Deoxygenation methods include saccharides such as sulfites and glucose, hydrazine, etc. These oxygen scavengers have been mainly used, but in these oxygen scavengers, substances that are extremely toxic, such as hydrazine, or decomposed and designated as deleterious substances, such as glucose. Since dozens of harmful components such as formic acid and acetaldehyde may be generated starting with formaldehyde, the use of oxygen scavengers that generate toxic substances such as hydrazine must be avoided.
As the oxygen scavenger other than these, for example, glycoheptonic acid or its sodium salt is used as Patent Document 1 as a supplemental agent for aqueous oxygen, and gluconic acid is used as Patent Document 2, for example. However, when using an oxygen scavenger, it is necessary to determine the input amount according to the dissolved oxygen concentration of the feed water. Concentration has the troublesome problem that external environment such as temperature must be taken into consideration.
In order to prevent corrosion, the present inventors have disclosed, as Patent Document 3, a water-soluble linear monosaccharide having 4 to 9 carbon atoms or a derivative as a salt or ester of a water-soluble linear monosaccharide as Patent Document 3 The terminal of the molecular structure of the saccharide is an —OH group or —COOH group, or a group sharing an —OH group and —COOH group, or a mixture of —OH group and —COOH group. In addition, an invariant anticorrosive agent for boilers that does not contain a -CO bond in the molecular structure is provided.
[0004]
On the other hand, various sparingly soluble salts are deposited on the scale in the pipe, but particularly common components include a hardness distribution scale such as calcium carbonate, a silica scale, and an iron scale. If the scale adheres, it causes serious troubles such as a decrease in thermal efficiency and blockage of piping.
In general, soft water boiler water uses raw water such as industrial water and underground water using soft water ion exchange resin to remove dissolved hardness, and this water is used as makeup water. Sometimes the silica component that is not exchanged or the hardness component that remains without being exchanged is deposited as a scale in the boiler pipe and the boiler can body during boiler operation, causing scale failure. In order to prevent these scale obstacles, maleic acid-based, acrylic acid-based, phosphonic acid-based and other polymer dispersants have been used.
[0005]
[Patent Document 1]
JP-A-6-25875 [Patent Document 2]
European Patent Application No. 272887 [Patent Document 3]
Japanese Patent Laid-Open No. 6-249880 [0006]
[Problems to be solved by the invention]
However, the anticorrosive film-forming agent disclosed in Patent Document 3 has high safety to the human body and the environment by using saccharides and does not turn brown in an alkaline aqueous solution. Considering the impact on the surface, there was a problem that the amount of use had to be reduced for safety and economy.
In addition, since cooling water systems and boiler water systems are operated with a combination of anticorrosives and scale inhibitors, there is a problem in that each water treatment agent must be managed and adjusted in an appropriate amount. It was.
The present invention has been made in view of the above-mentioned problems, and the subject thereof is a water treatment agent that is composed of a material that is highly safe to the human body and the environment, and has both an excellent corrosion prevention function and a scale prevention function. Thus, it is an object of the present invention to provide a water treatment agent capable of reducing the amount of use due to the influence on the drainage surface.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the invention of claim 1 is a mixture of sugar acid and D-glucitol, wherein the composition weight ratio of sugar acid to D-glucitol is within the range of 5 to 95% of sugar acid. It is a water treatment agent characterized by being.
The invention according to claim 2 is the water treatment agent according to claim 1, wherein polymaleic acid and a derivative thereof are added to the mixture.
The invention of claim 3 is a mixture of saccharide acid and D-glucitol, wherein the composition weight ratio of saccharide acid to D-glucitol is in the range of 10 to 90% of saccharide acid, and polymaleic acid and its derivatives are added thereto. It is a water treatment agent characterized by being added to a boiler water system.
The invention according to claim 4 is the water treatment agent according to claim 2 or 3, wherein the polymaleic acid and its derivative are added in a range of 10 to 300 mg / L.
[0008]
The present inventors have found that as a raw material of a water treatment agent having an anticorrosive function, there is a food additive in consideration of safety, or a sugar acid which is a substance known to have safety corresponding thereto. However, a mixture of sugar acid and D-glucitol improves the corrosion prevention function of the cooling water system and the boiler water system more than sugar acid alone, and further has a scale prevention function. The present invention has been conceived based on the finding that the treating agent can achieve both the functions of preventing corrosion and preventing scale. In addition, by adding polymaleic acid, which is considered to have a dispersing function, to a mixture of sugar acid and D-glucitol, the corrosion prevention is improved and the scale prevention function is greatly improved. The present inventors have also found that the use of this water treatment agent can prevent the corrosion and scale of the cooling water system and the boiler water system from being achieved, and the present invention has been conceived.
[0009]
Examples of the present invention will be specifically described below.
[Example 1]
The first embodiment of the present invention is a water treatment agent having an enhanced corrosion prevention function by mixing sugar acid and D-glucitol, which has an enhanced corrosion prevention function than that of a single sugar acid, It has been found to have scale prevention and is a water treatment agent having both functions.
In Example 1, a highly safe sugar acid and D-glucitol were used as an anticorrosive raw material, and a mixture of the two was used. The water treatment agent obtained by mixing the two was more than the simple substance of sugar acid or D-glucitol. The anti-corrosion function is improved. This will be described with reference to [Table 1] in FIG. 1 and [Graph 1] in FIG.
[Table 1] in FIG. 1 and [Graph 1] in FIG. 2 use SS-400, which is an iron material, as a test piece, and a commercially available product having a size of 2.0 mm × 15 mm × 30 mm. The container used for the corrosion test is a 500 mL fluororesin container, and 300 mL of ground water at room temperature is added to the container, and the corrosion rate for the iron corrosion investigation test piece SS-400 is set to 1 for the total concentration of sugar and D-glucitol. Adjusted to × 10 ^-3 mol / L, as shown in the left two columns of [Table 1] in Fig. 1, the state without any addition, the state with the addition of a single sugar acid, the sugar acid and D- The results show that the glucitol was added at different weight ratios and the D-glucitol simple substance was added, the groundwater was stirred with a stirrer, and the experiment was conducted continuously for 10 days. The mdd of the corrosion rate is mg / 1 dm ² (= 100 cm ² ) / 1 day of the metal damaged by corrosion.
[0010]
Here, the corrosion inhibition rate in [Table 1] in FIG. 1 was set to% of the value at which the corrosion rate in each experiment decreased with respect to the corrosion rate of 19 mdd when nothing was added.
In addition, the amount of scale adhered after the test is lightly washed with water, after removing moisture, dried overnight in a desiccator, then weighed, then the test piece is pickled to remove deposits, washed with water and dried. weighed test pieces again, the weight difference between the two is the scale deposition amount, which was converted to per surface area, and the unit is (mg / cm ^2/10 days).
Here, the scale inhibition rate was set to% of the value in which the scale adhesion amount in each experiment was reduced with respect to the scale adhesion amount of 25 mg when nothing was added.
From the graph 1 of FIG. 2 of this result, in Example 1, compared with the case of each drug of sugar acid and D-glucitol, the composition ratio of sugar acid to D-glucitol (hereinafter simply referred to as “sugar acid composition ratio”). In the range of 5 to 95%, the corrosion inhibition rate is improved by 15% compared to the case of sugar acid alone (sugar acid composition ratio 100%) and 5% than that of D-glucitol alone (sugar acid composition ratio 0%). %improves. In use, preferably, the corrosion inhibition rate is further improved in the range of the sugar acid composition ratio of 20 to 90%, more preferably further improved in the range of the sugar acid composition ratio of 60 to 80%, most preferably. The sugar acid composition ratio is around 70%, which is 36% higher than that of sugar acid alone and 26% higher than that of D-glucitol alone.
[0011]
Further, the scale inhibition rate is improved to 4 to 16% compared to the case where none of [Table 1] and [Graph 1] is added, but the corrosion inhibition rate is also in the range of the sugar acid composition ratio of 5 to 95%. improvement to the the monitor, the scale inhibition rate was also increased to 4-12%, in the range of sugar composition ratio 10% to 80%, scale inhibition rate is further increased to 8% to 12%.
Incidentally, as similar to the sugar acid, tartaric acid, alginic acid, polyacrylic acid and salts thereof, or the like derivative is considered, may be changed to those as long as it has the same effect, also, D- Similar to glucitol may be glycerin, erythritol, arabitol, ribitol, fucose, galactitol, sorbitol, peptitol, octitol, polyethylene glycol, polyoxypropylene glycol and their derivatives, etc. If it is a thing, you may change to these.
[0012]
[Example 2]
Next, the present inventors have generally used a polymer dispersant as a water treatment agent for scale prevention and sludge dispersion in cooling and heating water systems and boiler water systems, and the sugar acid and D-glucitol of Example 1 are sometimes used. It was thought that the scale prevention function could be improved by adding a polymaleic acid-based polymer dispersant to the water treatment agent of the mixture.
(1) Experimental example 1
First, in order to investigate the appropriate amount of polymaleic acid, the amount of polymaleic acid added was changed to determine the range of the appropriate amount. In this experiment, select the sugar acid composition of 40% in the range of suitable values of sugar acids and D- glucitol that in Example 1 described above, and the sacrificial inhibition rate the dispersant concentration in the range of 0~500mg / L The scale inhibition rate was examined, and the corrosion inhibition rate and scale inhibition rate were added as an evaluation index to obtain a comprehensive evaluation. This corrosion inhibition rate (%) + scale inhibition rate (%) was expressed as [ Table 2].
From [Table 2] in FIG. 3, it can be seen that the anti-corrosion inhibition rate and the scale inhibition rate are appropriate in the range of 10 to 300 mg / L of polymaleic acid as a dispersant.
[0013]
(2) Experimental example 2
Next, the relationship between the polymaleic acid, which is a dispersant, and the composition change of the mixture of sugar acid and D-glucitol in Example 1 was examined. As a result, an unexpected fact was grasped.
Based on the experimental conditions in (1) above, the amount of polymaleic acid added is determined, but the amount to be used is as low as possible in the range of 10 to 300 mg / L where the corrosion inhibition rate and scale inhibition rate are improved. Of polymaleic acid.
That is, in the second embodiment of the present invention, polymaleic acid is added to a mixture of sugar acid and D-glucitol, but the polymaleic acid as a dispersant is 20 mg / L using a commercially available product. The addition amount of sugar acid and D-glucitol or a mixture thereof was 100 mg / L. Unless otherwise specified, the experimental conditions in Example 1 are the same.
The results of this experiment are shown in [Table 3] in FIG. 4 and [Graph 2] in FIG. 5, but the scale inhibition rate is higher than that in Example 1 and D-glucitol alone, which is the maximum value in Example 1. In Example 2, the inhibition rate is at least doubled over the entire area in Example 2, and 8% in Example 1 is about 8% in the vicinity of 40% of sugar acid, and 70% in Table 3 of Example 2 is 8%. Further, the corrosion inhibition rate is reliably improved as compared with Example 1 in the range of 10% to 40% of the sugar acid composition than the corrosion inhibition rate of 42% with the saccharide acid alone.
In this example, polymaleic acid was used as the scale dispersant, but polymaleic acid and derivatives thereof may be used, and polycarboxyethylphosphinic acid, polyacrylic acid and derivatives, and the like may be used.
As described above, in Example 2, when polymaleic acid and its derivatives are added to a water treatment agent in which sugar acid and D-glucitol are mixed, the scale inhibition rate is dramatically improved and the corrosion inhibition rate is also improved.
[0014]
(3) Experimental example 3
Furthermore, in order to approach the boiler conditions of high-temperature water, simulated boiler water was prepared and circulated for 10 consecutive days at a reflux temperature of 100 ° C., and the corrosion rate and the amount of scale adhered were simultaneously investigated. The high temperature water in the boiler water system is usually in the range of about 80 to 250 ° C., but the corrosion rate and the amount of scale adhesion in the 10-day circulation in this range can be estimated from the reflux experiment at 100 ° C., so the experiment is easy. The simulated boiler water at 100 ° C was used.
The composition of the simulated boiler water is: acid consumption (pH 4.8) 300 (mgCaCO ₃ / L), chloride ion concentration 500 (mgCl ⁻ / L), silica 300 (mgSiO ₂ / L), total iron (5 mgFe / L) ), Sulfate ion (500 mg SO42- / L), electrical conductivity 50 (mS / m), pH about 10.5, and the effect is the corrosion inhibition rate (%) + scale inhibition rate (%) as one index of evaluation The results are shown in [Table 4] in FIG. 6 and [Graph 3] in FIG.
From [Graph 3] in FIG. 7, the corrosion inhibition effect was improved when the sugar acid composition ratio was 10 to 90%.
Thus, it can be seen that the improvement in scale inhibition rate and corrosion inhibition rate of Example 2 at room temperature described above is the same tendency at high temperatures, and particularly in the environment of high-temperature water under boiler conditions, sugar acid and D -It was found that the scale inhibition rate and the corrosion inhibition rate were remarkably improved over the entire region as compared with the case of glucitol alone, and in particular, compared with Example 1, the sugar acid alone was around 20% of the sugar acid composition. It can be seen that the corrosion inhibition rate is actually 100%, which is 47% higher than the 53% corrosion inhibition rate.
Therefore, in the water treatment agent of Example 2, the composition weight ratio of saccharide acid to D-glucitol is improved in the function while having both the function of inhibiting the scale and inhibiting the corrosion in the range of 10 to 90% of the saccharide acid. Thus, it is understood that it is optimal to use in a boiler that uses high-temperature water, not to mention at room temperature.
[0015]
(4) Experimental example 4
An alkaline agent, a dispersant, and an anticorrosive agent (sugar acid 40% -D-glucitol) are added to pure water in a mixture ratio of the sugar acid and D-glucitol of Example 1 at a general addition ratio as a canning agent, Good result of about 200 ° C-1.568 Mpa, 10-fold concentration, 10% blow, 100 hours continuous operation, corrosion rate of 5 mdd, scale, no sludge with an experimental boiler with 100 mg / L added to soft water was gotten.
[0016]
It should be noted that the present invention is not limited to the above examples as long as the characteristics of the present invention are not impaired. For example, phosphate, polymerized phosphate, phosphonate, Pyrophosphates, phosphate esters, amines (eg hydrazine, morpholine, octadecylamine, jetylaminoethanol, cyclohexylamine, propanolamine, aminoethanol, diethylhydroxyamine, aminopropanolamine), sulfites, molybdates, Substances such as a chlorine-based disinfectant, an organic nitrogen-based disinfectant, nitrite, an inorganic alkali agent, and a polymer dispersant may be used in combination as appropriate.
[0017]
【The invention's effect】
As described above, according to the present invention, sugar acid and D-glucitol are food additives or substances that are known to have safety corresponding thereto, and thus are highly safe as water treatment agents, In addition, by mixing sugar acid and D-glucitol, it has the effect of improving the corrosion prevention function of cooling heating water system and boiler water system more than the simple substance of sugar acid and D-glucitol. effect since even have together, since the need of a single treatment agent if put adjusted decide premixed composition ratio, it is not necessary to blend adjusting anticorrosive and a scale inhibitor, that management is facilitated In addition, the addition of polymaleic acid and its derivatives has the effect of improving corrosion prevention and dramatically improving the scale prevention function. Which in high temperature water environments is an effect that corrosion protection and scale prevention function is further improved.
[Brief description of the drawings]
FIG. 1 is a table of [Table 1] of corrosion inhibition rate and scale inhibition rate with respect to the mixing ratio of sugar acid and D-glucitol in Example 1 of the present invention.
FIG. 2 is a diagram representing [Table 1] in FIG. 1 as [Graph 1].
FIG. 3 is a table of [Table 2] of corrosion inhibition rate and scale inhibition rate corresponding to changes in the amount of polymaleic acid added in Example 2 of the present invention.
FIG. 4 is a table of [Table 3] of corrosion inhibition rate and scale inhibition rate with respect to the mixing ratio of sugar acid and D-glucitol when polymaleic acid is added in Example 2 of the present invention. 4 is a diagram showing [Table 3] in FIG. 4 as [Graph 2].
FIG. 6 is a table of [Table 4] of corrosion inhibition rate and scale inhibition rate corresponding to changes in the amount of polymaleic acid added in an environment of high-temperature water in Example 2 of the present invention.
FIG. 7 is a diagram showing [Table 4] in FIG. 6 as [Graph 3].

Claims (4)

  A water treatment agent, which is a mixture of sugar acid and D-glucitol, wherein the composition weight ratio of sugar acid to D-glucitol is in the range of 5 to 95% of sugar acid.   The water treatment agent according to claim 1, wherein polymaleic acid and a derivative thereof are added to the mixture.   A mixture of sugar acid and D-glucitol, the composition weight ratio of sugar acid to D-glucitol being within the range of 10 to 90% of sugar acid, to which polymaleic acid and its derivatives are added and used in boiler water system A water treatment agent characterized by that. The water treatment agent according to claim 2 or 3, wherein the polymaleic acid and its derivative are added in a range of 10 to 300 mg / L.

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